Entity Central Index Key Document and entity information. Document And Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Ex Transition Period Entity Ex Transition Period Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Statement Of Financial Position [Abstract] Assets Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Marketable securities Available For Sale Securities Debt Securities Current Income tax receivable Income Taxes Receivable Other receivables Other Receivables Net Current Prepaid expenses Prepaid Expense Current Restricted cash, current Restricted Cash Current Total current assets Assets Current Property and equipment, net Property Plant And Equipment Net Restricted cash Restricted Cash Noncurrent Total assets Assets Liabilities and stockholders’ equity Liabilities And Stockholders Equity [Abstract] Current liabilities: Liabilities Current [Abstract] Accounts payable and accrued expenses Accounts Payable And Accrued Liabilities Current Current portion of deferred revenue Contract With Customer Liability Current Total current liabilities Liabilities Current Deferred revenue, non-current Contract With Customer Liability Noncurrent Deferred lease obligation Deferred Rent Credit Noncurrent Commitments and contingencies (Note 15) Commitments And Contingencies Stockholders’ equity: Stockholders Equity [Abstract] Preferred stock; $0.001 par value; 5,000,000 shares authorized at September 30, 2018 and December 31, 2017, zero shares issued and outstanding at September 30, 2018 and December 31, 2017 Preferred Stock Value Common stock; $0.001 par value; 100,000,000 shares authorized at September 30, 2018 and December 31, 2017, 39,389,515 shares and 32,662,255 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively Common Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Accumulated deficit Retained Earnings Accumulated Deficit Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income Loss Net Of Tax Total stockholders’ equity Stockholders Equity Total liabilities and stockholders’ equity Liabilities And Stockholders Equity Preferred stock, par value Preferred Stock Par Or Stated Value Per Share Preferred stock, shares authorized Preferred Stock Shares Authorized Preferred stock, shares issued Preferred Stock Shares Issued Preferred stock, shares outstanding Preferred Stock Shares Outstanding Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, shares authorized Common Stock Shares Authorized Common stock, shares issued Common Stock Shares Issued Common stock, shares outstanding Common Stock Shares Outstanding Income Statement [Abstract] Statement [Table] Statement [Table] Product and Service Product Or Service [Axis] Product and Service Products And Services [Domain] License and milestone fees. License and Milestone Fees [Member] License And Milestone Fees [Member] Collaborative revenue. Collaborative Revenue [Member] Collaborative Revenue [Member] Clinical compound revenue. Clinical Compound Revenue [Member] Clinical Compound Revenue [Member] Statement [Line Items] Statement [Line Items] Revenue: Revenues [Abstract] Total revenue Revenue From Contract With Customer Excluding Assessed Tax Operating expenses: Operating Expenses [Abstract] Research and development Research And Development Expense General and administrative General And Administrative Expense Total operating expenses Operating Expenses Operating loss Operating Income Loss Other income Other Nonoperating Income Expense Loss before benefit from income taxes Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest Benefit from income taxes Income Tax Expense Benefit Net loss Net Income Loss Net loss per share: Earnings Per Share Basic And Diluted [Abstract] Basic and Diluted Earnings Per Share Basic And Diluted Weighted average shares: Weighted Average Number Of Shares Outstanding [Abstract] Basic and Diluted Weighted Average Number Of Share Outstanding Basic And Diluted Other comprehensive income (loss), net of tax of $0: Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent [Abstract] Change in unrealized gains (losses) on available-for- sale marketable securities Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax Total comprehensive loss Comprehensive Income Net Of Tax Other comprehensive income (loss), tax Other Comprehensive Income Loss Tax Adjustments to additional paid in capital modification of equity awards. Sale of common stock under a license agreement. Statement Of Stockholders Equity [Abstract] Additional Paid-In Capital [Member] Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Stock [Member] Common Stock [Member] Additional Paid-In Capital [Member] Additional Paid In Capital [Member] Accumulated Deficit [Member] Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) [Member] Accumulated Other Comprehensive Income [Member] Sale of Stock Subsidiary Sale Of Stock [Axis] Sale of Stock Sale Of Stock Name Of Transaction [Domain] Follow on public offering. Follow-on Public Offering [Member] Follow On Public Offering [Member] Balance, Value Balance, Shares Shares Outstanding Sale of common stock, net of underwriting discounts and commissions and offering expenses, Value Stock Issued During Period Value New Issues Sale of common stock, net of underwriting discounts and commissions and offering expenses, Shares Stock Issued During Period Shares New Issues Sale of common stock under license agreement, Value Stock Issued During Period Value Under License Agreement Sale of common stock under a license agreement Sale of common stock under license agreement, Shares Stock Issued During Period Shares Under License Agreement Stock-based compensation expense Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Modification of equity awards Adjustments To Additional Paid In Capital Modification Of Equity Awards Shares issued upon exercise of stock options, Value Stock Issued During Period Value Stock Options Exercised Shares issued upon exercise of stock options, Shares Stock Issued During Period Shares Stock Options Exercised Cumulative effect adjustment upon adoption of ASU 2016-09 New Accounting Pronouncement Or Change In Accounting Principle Effect Of Adoption Quantification Net loss Other comprehensive income Other Comprehensive Income Loss Net Of Tax Balance, Value Balance, Shares Sale of common stock, per share Shares Issued Price Per Share Underwriting discounts and commissions and offering expenses Adjustments To Additional Paid In Capital Stock Issued Issuance Costs Modification of equity awards. Deferred Rent Liability Expense Benefit Proceeds from sale of common stock under license agreement. Statement Of Cash Flows [Abstract] Operating activities Net Cash Provided By Used In Operating Activities [Abstract] Net loss Profit Loss Adjustments to reconcile net loss to net cash provided by (used in) operating activities: Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Stock-based compensation expense Share Based Compensation Modification of equity awards Modification Of Equity Awards Depreciation and amortization Depreciation Depletion And Amortization Amortization/accretion of available-for-sale marketable securities Accretion Amortization Of Discounts And Premiums Investments Realized loss (gain) on sale of available-for-sale marketable securities Debt Securities Available For Sale Realized Gain Loss Realized gain on sale of property and equipment Gain Loss On Sale Of Property Plant Equipment Deferred rent costs Deferred Rent Liability Expense Benefit Deferred revenue Increase Decrease In Contract With Customer Liability Changes in operating assets and liabilities: Increase Decrease In Operating Capital [Abstract] Income tax receivable Increase Decrease In Income Taxes Receivable Other receivables Increase Decrease In Other Receivables Prepaid expenses Increase Decrease In Prepaid Expense Accounts payable and accrued expenses Increase Decrease In Accounts Payable And Accrued Liabilities Net cash provided by (used in) operating activities Net Cash Provided By Used In Operating Activities Investing activities Net Cash Provided By Used In Investing Activities [Abstract] Proceeds from maturities of available-for-sale marketable securities Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities Proceeds from sale of available-for-sale marketable securities Proceeds From Sale Of Available For Sale Securities Debt Purchases of available-for-sale marketable securities Payments To Acquire Available For Sale Securities Debt Purchases of property and equipment Payments To Acquire Property Plant And Equipment Proceeds from sale of property and equipment Proceeds From Sale Of Property Plant And Equipment Net cash used in investing activities Net Cash Provided By Used In Investing Activities Financing activities Net Cash Provided By Used In Financing Activities [Abstract] Proceeds from sale of common stock in a follow-on public offering, net of issuance costs Proceeds From Issuance Of Common Stock Proceeds from the sale of common stock under license agreement Proceeds From Sale Of Common Stock Under License Agreement Proceeds from the exercise of stock options Proceeds From Stock Options Exercised Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Net increase (decrease) in cash, cash equivalents and restricted cash Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect Cash, cash equivalents and restricted cash at beginning of period Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Cash, cash equivalents and restricted cash at end of period Organization Consolidation And Presentation Of Financial Statements [Abstract] Business Nature Of Operations Basis of Presentation Basis Of Accounting Investments Debt And Equity Securities [Abstract] Available-for-Sale Marketable Securities Investments In Debt And Marketable Equity Securities And Certain Trading Assets Disclosure [Text Block] Equity [Abstract] Accumulated Other Comprehensive Income (Loss) Comprehensive Income Note [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Receivables [Abstract] Restricted Cash Restricted Assets Disclosure [Text Block] Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract] Prepaid Expenses Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Text Block] Payables And Accruals [Abstract] Accounts Payable and Accrued Expenses Accounts Payable And Accrued Liabilities Disclosure [Text Block] Stockholders' Equity Stockholders Equity Note Disclosure [Text Block] Collaboration and Licensing Agreements Collaborative Arrangement Disclosure [Text Block] Revenue Recognition [Abstract] Revenue Recognition Revenue From Contract With Customer [Text Block] Earnings Per Share [Abstract] Net Loss Per Share Earnings Per Share [Text Block] Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Stock-Based Compensation Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Subsequent Events [Abstract] Subsequent Event Subsequent Events [Text Block] Use of Estimates Use Of Estimates Significant Accounting Policies Basis Of Accounting Policy Policy [Text Block] Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Summary of Available-for-Sale Marketable Securities by Major Type of Security Schedule Of Available For Sale Securities Reconciliation Table [Text Block] Schedule of Amortized Cost and Fair Values of Marketable Debt Securities by Contractual Maturity Investments Classified By Contractual Maturity Date Table [Text Block] Schedule of Fair Values and Continuous Unrealized Loss Positions of Available-for-Sale Marketable Securities Debt Securities Available For Sale Unrealized Loss Position Fair Value Table [Text Block] Summary of Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax, from Unrealized Gains (Losses) on Available-for-Sale Marketable Securities Schedule Of Accumulated Other Comprehensive Income Loss Table [Text Block] Schedule of Reclassification Out of Accumulated Other Comprehensive Income Reclassification Out Of Accumulated Other Comprehensive Income Table [Text Block] Summary of Financial Assets Measured at Fair Value on Recurring Basis Fair Value Assets Measured On Recurring Basis [Text Block] Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash Schedule Of Restricted Cash And Cash Equivalents [Text Block] Schedule of Accounts Payable and Accrued Expenses Schedule Of Accounts Payable And Accrued Liabilities Table [Text Block] Computation of Denominators Used in Net Loss per Share Schedule Of Weighted Average Number Of Shares Table [Text Block] Computation of Basic and Diluted Net Loss per Share Schedule Of Earnings Per Share Basic And Diluted Table [Text Block] Measurement Basis Fair Value By Measurement Basis [Axis] Fair Value Disclosure Item Amounts [Default] Portion At Fair Value Fair Value Disclosure [Member] Fair Value Measurement Fair Value Disclosure Item Amounts [Domain] Re-Measurement [Member] Change During Period Fair Value Disclosure [Member] Title of Individual Title Of Individual [Axis] Relationship to Entity Title Of Individual With Relationship To Entity [Domain] Non-employee. Non-employee Consultants [Member] Nonemployee [Member] Summary of Assumptions Used in Black-Scholes Option Pricing Model Schedule Of Share Based Payment Award Stock Options Valuation Assumptions Table [Text Block] Summary of Compensation Expense Relating to Stock Options Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block] Summary of Stock Option Activity Schedule Of Share Based Compensation Stock Options Activity Table [Text Block] Schedule of Contractual Obligations and Commitments Consisting of Future Minimum Lease Payments Contractual Obligation Fiscal Year Maturity Schedule Table [Text Block] Accounting Policies [Abstract] Nature Of Business [Line Items] Nature Of Business [Table] Nature Of Business [Table] Nature Of Business [Table] Related Party Transaction Related Party Transaction [Axis] Related Party Transaction Related Party Transaction [Domain] Vifor (International) Ltd. Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] Vifor International Ltd [Member] Nature Of Business [Line Items] Nature Of Business [Line Items] Date of formation Entity Incorporation Date Of Incorporation Aggregate net proceeds since inception of the company received from equity and debt financings. Upfront and milestone payments earned in connection with license agreements. Proceeds from equity and debt financing Aggregate Net Proceeds From Equity Financing And Issuance Of Debt Upfront and milestone payments received in connection with license agreements Upfront And Milestone Payments Earned In Connection With License Agreements Proceeds from sale of common stock in connection with license agreement Common stock, shares issued Unrestricted cash and cash equivalents and marketable securities Cash Cash Equivalents And Short Term Investments Accumulated deficit Net loss Net cash provided by (used in) operating activities Schedule Of Available For Sale Securities [Table] Schedule Of Available For Sale Securities [Table] Investment Type Investment Type [Axis] Investments Investment Type Categorization [Member] Money Market Funds [Member] Money Market Funds [Member] U.S. Treasury Securities [Member] U S Treasury Securities [Member] U.S. Government Agency Obligations [Member] U S Government Corporations And Agencies Securities [Member] Corporate Bonds [Member] Corporate Bond Securities [Member] Commercial Paper [Member] Commercial Paper [Member] Schedule of Available-for-sale Securities [Line Items] Schedule Of Available For Sale Securities [Line Items] Amortized Cost Available For Sale Debt Securities Amortized Cost Basis Gross Unrealized Gains Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax Gross Unrealized Losses Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax Estimated Fair Value Amortized Cost of marketable debt securities, contractual maturity, Less than one year Available For Sale Securities Debt Maturities Within One Year Amortized Cost Fair value of marketable debt securities, contractual maturity, Less than one year Available For Sale Securities Debt Maturities Within One Year Fair Value Realized loss Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Fair Value Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Gross Unrealized Losses Available For Sale Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss Available-for-sale marketable securities, continuous unrealized loss position, Fair Value Available For Sale Securities Continuous Unrealized Loss Position Fair Value Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss Available for sale securities qualitative disclosure number of positions. Number of available-for-sale marketable securities in unrealized loss positions Debt Securities Available For Sale Unrealized Loss Position Number Of Positions Total number of positions Available For Sale Securities Qualitative Disclosure Number Of Positions Other-than-temporary impairments on securities Debt Securities Available For Sale Realized Loss Excluding Other Than Temporary Impairment Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract] Accumulated Other Comprehensive Income Loss [Table] Accumulated Other Comprehensive Income Loss [Table] Accumulated Other Comprehensive Income Loss [Line Items] Accumulated Other Comprehensive Income Loss [Line Items] Other comprehensive income before reclassifications Other Comprehensive Income Loss Before Reclassifications Net Of Tax Amount reclassified from accumulated other comprehensive loss (income) Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax Net current period other comprehensive income (loss) Reclassification Out Of Accumulated Other Comprehensive Income [Table] Reclassification Out Of Accumulated Other Comprehensive Income [Table] Accumulated Net Unrealized Investment Gain (Loss) Attributable to Parent [Member] Accumulated Net Unrealized Investment Gain Loss [Member] Reclassification out of Accumulated Other Comprehensive Income Reclassification Out Of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income Reclassification Out Of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Member] Reclassification Out Of Accumulated Other Comprehensive Income [Member] Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items] Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items] Benefit from income taxes Net of tax Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Asset Class Fair Value By Asset Class [Axis] Asset Class Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation By Asset Class [Domain] U.S. Treasury Securities [Member] Fair Value Hierarchy and NAV Fair Value By Fair Value Hierarchy Level [Axis] Fair Value Hierarchy and NAV Fair Value Measurements Fair Value Hierarchy [Domain] Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Fair Value Inputs Level1 [Member] Significant Other Observable Inputs (Level 2) [Member] Fair Value Inputs Level2 [Member] Significant Unobservable Inputs (Level 3) [Member] Fair Value Inputs Level3 [Member] Measurement Frequency Fair Value By Measurement Frequency [Axis] Fair Value, Measurement Frequency Fair Value Measurement Frequency [Domain] Recurring [Member] Fair Value Measurements Recurring [Member] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Financial assets Assets Fair Value Disclosure [Abstract] Cash and cash equivalents Cash And Cash Equivalents Fair Value Disclosure Available-for-sale marketable securities Restricted cash Restricted Cash And Cash Equivalents Noncurrent Total financial assets Assets Fair Value Disclosure Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Table] Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] Purchases of financial assets Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases Sales of financial assets Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Sales Maturities of financial assets Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Settlements Unrealized gains Available For Sale Debt Securities Gross Unrealized Gain Unrealized losses Available For Sale Debt Securities Gross Unrealized Loss Transfer of financial asset into level 3 of fair value Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Net Fair value assets level 2 to level 1 transfers Fair Value Assets Level2 To Level1 Transfers Amount Fair value assets level 1 to level 2 transfers Fair Value Assets Level1 To Level2 Transfers Amount Letters of credit amount outstanding date. Lease expiration year. Letters of Credit Reduced Outstanding Amount Based Upon Request Cash And Cash Equivalents [Abstract] Schedule Of Restricted Cash And Cash Equivalents [Table] Schedule Of Restricted Cash And Cash Equivalents [Table] Restricted Cash and Cash Equivalents Restricted Cash And Cash Equivalents Cash And Cash Equivalents [Axis] Cash and Cash Equivalents Restricted Cash And Cash Equivalents Cash And Cash Equivalents [Member] Money market fund for Stamford lease. Stamford Lease [Member] Money Market Fund For Stamford Lease [Member] Restricted Cash and Cash Equivalents Items [Line Items] Restricted Cash And Cash Equivalents Items [Line Items] Letter of credit, remaining amount Letters Of Credit Outstanding Amount Letter of credit, through the end of lease term Letters Of Credit Reduced Outstanding Amount Based Upon Request Letter of credit, remaining amount date Letters Of Credit Amount Outstanding Date Operating lease, expiration year Lease Expiration Year Restricted cash balance Restricted cash in current assets Restricted cash, long-term assets Total cash, cash equivalents, and restricted cash shown in the Condensed Statements of Cash Flows Amount of asset related to consideration paid in advance for research and development expenses that provide economic benefits within a future period of one year or the normal operating cycle, if longer. Prepaid R&D clinical costs Prepaid Research And Development Expenses Prepaid insurance Prepaid Insurance Other prepaid costs Other Prepaid Expense Current Carrying value as of the balance sheet date of obligations incurred through that date and payable for costs related to research and development projects. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accounts payable Accounts Payable Current Accrued research projects Accrued Research Projects Accrued professional fees Accrued Professional Fees Current Accrued compensation and benefits Accrued Employee Benefits Current Accrued other Other Accrued Liabilities Current Total Proceeds from issuance of common stock net of underwriting discounts and offering expenses. Subsidiary Or Equity Method Investee Sale Of Stock By Subsidiary Or Equity Investee [Table] Subsidiary Or Equity Method Investee Sale Of Stock By Subsidiary Or Equity Investee [Table] Underwriter's Over-Allotment [Member] Over Allotment Option [Member] Range Range [Axis] Range Range [Member] Maximum [Member] Maximum [Member] Minimum [Member] Minimum [Member] Vifor Fresenius Medical Care Renal Pharma Limited. Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] Vifor Fresenius Medical Care Renal Pharma Limited [Member] Subsidiary, Sale of Stock [Line Items] Subsidiary Sale Of Stock [Line Items] Proceeds from issuance of common stock net of underwriting discounts and offering costs Proceeds From Issuance Of Common Stock Net Of Underwriting Discounts And Offering Expenses Underwriting discounts, commission and offering expenses Payments Of Stock Issuance Costs Third party cost for clinical development threshold amount. Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table] Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table] Type of Arrangement and Non-arrangement Transactions Type Of Arrangement [Axis] Arrangements and Non-arrangement Transactions Arrangements And Nonarrangement Transactions [Member] Regulatory and commercial milestones. Regulatory and Commercial Milestones [Member] Regulatory And Commercial Milestones [Member] Regulatory milestones. Regulatory Milestones [Member] Regulatory Milestones [Member] Tiered commercial milestones. Tiered Commercial Milestones [Member] Tiered Commercial Milestones [Member] Maruishi Pharmaceutical Co., Ltd. Maruishi Pharmaceutical Co., Ltd. [Member] Maruishi Pharmaceutical Company Limited [Member] Sub-License Fee [Member] License [Member] Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items] Third-party cost for clinical development Third Party Cost For Clinical Development Threshold Amount Number of performance obligations for revenue recognized. Number of performance obligations for revenue recognized Number Of Performance Obligations For Revenue Recognized Revenue performance obligation upfront payment received. Premium from sale of stock. Closing prices of company common stock description. Non-refundable, non-creditable upfront payment Revenue Performance Obligation Upfront Payment Received Purchase of common stock value Purchase common stock per share amount Closing prices of company common stock description Closing Prices Of Company Common Stock Description Premium from sale of stock Premium From Sale Of Stock Potential milestone payments receivable. Milestone payments receivable Potential Milestone Payments Receivable Number of combined performance obligations for revenue recognized. Contract liabilities Contract With Customer Liability Number of combined performance obligations for revenue recognized Number Of Combined Performance Obligations For Revenue Recognized Termination notice effective period. Number of days to terminate agreement upon material breach. Number of days to terminate agreement Number Of Days To Terminate Agreement Upon Material Breach Termination notice effective period Agreement Termination Notice Effective Period Revenue from contract with customer Cost of clinical compound sale related to research and development expense. Cost of clinical compound related to R&D expense Cost Of Clinical Compound Sale Related To Research And Development Expense Revenue Recognition Multiple Deliverable Arrangements [Table] Revenue Recognition Multiple Deliverable Arrangements [Table] Research and Development Arrangement, Contract to Perform for Others, Type Research And Development Arrangement Contract To Perform For Others By Type [Axis] Research and Development Arrangement, Contract to Perform for Others, Type Research And Development Arrangement Contract To Perform For Others Type [Domain] License agreement with vifor fresenius medical care renal pharma limited. VFMCRP Agreement [Member] License Agreement With Vifor Fresenius Medical Care Renal Pharma Limited [Member] License agreement with Maruishi Pharmaceutical Company Limited and Chong Kun Dang Pharmaceutical Corporation. Maruishi and CKDP Agreements [Member] License Agreement With Maruishi Pharmaceutical Company Limited And Chong Kun Dang Pharmaceutical Corporation [Member] License agreement with Maruishi Pharmaceutical Company Limited. Maruishi Agreement [Member] License Agreement With Maruishi Pharmaceutical Company Limited [Member] Clinical development and regulatory milestones. Clinical Development and Regulatory Milestones [Member] Clinical Development And Regulatory Milestones [Member] One-time sales milestone. One-time Sales Milestone [Member] One Time Sales Milestone [Member] License agreement with Chong Kun Dang Pharmaceutical. CKDP Agreement [Member] License Agreement With Chong Kun Dang Pharmaceutical [Member] License [Member] Research and development services. R&D Services [Member] Research And Development Services [Member] Royalty [Member] Royalty [Member] Revenue Recognition Multiple Deliverable Arrangements [Line Items] Revenue Recognition Multiple Deliverable Arrangements [Line Items] Deferred revenue, current Deferred revenue, non current Receivables Accounts Receivable Net Other assets Other Assets Deferred revenue Remaining performance obligations Revenue Remaining Performance Obligation Number of performance obligations for revenue recognized Upfront payment Upfront license fee including premium of sale of stock. Upfront non-refundable, non-creditable license fee and premium from sale of stock Upfront License Fee Including Premium Of Sale Of Stock Remaining potential consideration Revenue from contract with customer Revenue From Contract With Customer Including Assessed Tax Estimated selling price Revenue Recognition Multiple Deliverable Arrangements Determination Of Selling Price Amount Remaining performance obligation, expected timing of satisfaction, year Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Year1 Number of milestone event probable of occurrence or achieved. Number of milestone event probable of occurrence or achieved Number Of Milestone Event Probable Of Occurrence Or Achieved Basic: Earnings Per Share Basic [Abstract] Weighted average common shares outstanding Weighted Average Number Of Shares Outstanding Basic Diluted: Earnings Per Share Diluted [Abstract] Weighted average common shares outstanding - Basic Common stock options Incremental Common Shares Attributable To Share Based Payment Arrangements Denominator for diluted net loss per share Weighted Average Number Of Diluted Shares Outstanding Weighted-average common shares outstanding: Net loss per share, Basic and Diluted Schedule Of Earnings Per Share Diluted By Common Class [Table] Schedule Of Earnings Per Share Diluted By Common Class [Table] Antidilutive Securities Antidilutive Securities Excluded From Computation Of Earnings Per Share By Antidilutive Securities [Axis] Antidilutive Securities, Name Antidilutive Securities Name [Domain] Employee Options [Member] Employee Stock Option [Member] Restricted Stock Units [Member] Restricted Stock Units R S U [Member] Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items] Earnings Per Share Diluted [Line Items] Anti-dilutive common stock equivalents Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Number of incentive stock options that may be granted after the tenth anniversary of the 2014 Equity Incentive Plan. Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Plan Name Plan Name [Axis] Plan Name Plan Name [Domain] Two Thousand And Fourteen Equity Incentive Plan [Member] 2014 Equity Incentive Plan [Member] Two Thousand And Fourteen Equity Incentive Plan [Member] Employees. Employees [Member] Employees [Member] Board of directors. Board of Directors [Member] Board Of Directors [Member] Vesting Vesting [Axis] Vesting Vesting [Domain] Share-Based Compensation Award, Tranche One [Member] Share Based Compensation Award Tranche One [Member] Share-based Compensation Award, Tranche Two [Member] Share Based Compensation Award Tranche Two [Member] Award Type Award Type [Axis] Equity Award Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Incentive Stock Options [Member] Incentive Stock Options [Member] Incentive Stock Options [Member] Executive Officers [Member] Executive Officer [Member] Non-employee Consultants [Member] Adjustments for New Accounting Pronouncements Adjustments For New Accounting Pronouncements [Axis] Type of Adoption Type Of Adoption [Member] ASU 2016-09 [Member] Accounting Standards Update201609 [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Number of stock options that may be granted after the tenth anniversary of the 2014 Plan Share Based Compensation Arrangement By Share Based Payment Award Number Of Stock Options That May Be Granted Percentage of vested shares on first anniversary of grant date Sharebased Compensation Arrangement By Sharebased Payment Award Award Vesting Rights Percentage Vesting period of awards granted Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1 Term of awards granted Sharebased Compensation Arrangement By Sharebased Payment Award Expiration Period On January 1 of each year from January 1, 2015 through /January 1, 2024, the number of shares reserved for issuance under the 2014 Equity Incentive Plan automatically increases by an amount of shares which is calculated as 3% of the shares of capital stock outstanding on the preceding December 31. Annual increases in number of shares reserved for issuance as a percentage of shares of capital stock outstanding through January 1, 2024 Annual Increase In Number Of Shares Reserved For Issuance As Percentage Of Shares Of Capital Stock Outstanding Share-based compensation arrangement by share-based payment award, number of shares authorized Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized Share based compensation arrangement by share based payment award equity instruments other than options number of performance target achieved. Restricted stock units, granted Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Restricted stock units, grant date fair value Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value Number of performance targets achieved Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Number Of Performance Target Achieved Restricted stock units, vested Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Compensation expense Allocated Share Based Compensation Expense Options granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross Non-employee stock option. Nonemployee Options [Member] Non Employee Stock Option [Member] Risk-free interest rate, minimum Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate Minimum Risk-free interest rate, maximum Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate Maximum Expected volatility, minimum Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate Minimum Expected volatility Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate Expected volatility, maximum Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate Maximum Expected dividend yield Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate Expected life of options (in years) Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 Fair value of options granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value Risk-free interest rate Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate Share based compensation arrangement by share based payment award options outstanding as re-measured during the vesting period of each tranche weighted average fair value. Weighted average fair values of outstanding options Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding As Remeasured During The Vesting Period Of Each Tranche Weighted Average Fair Value Cumulative-effect adjustment to stockholders' equity Cumulative Effect Of New Accounting Principle In Period Of Adoption Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table] Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table] Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] Research and Development [Member] Research And Development Expense [Member] General and Administrative [Member] General And Administrative Expense [Member] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] Total stock option expense Share based compensation arrangement by share based payment award compensation cost including effect of re-measurement of fair value. Total stock option expense including effect of re-measurement of fair value Share Based Compensation Arrangement By Share Based Payment Award Compensation Cost Including Effect Of Re Measurement Of Fair Value Number of Options, Outstanding at December 31, 2017 Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number Number of Options, Granted Number of Options, Exercised Number of Options, Expired Share Based Compensation Arrangement By Share Based Payment Award Options Expirations In Period Number of Options, Forfeited Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period Number of Options, Outstanding at June 31, 2018 Number of Options, Options exercisable at June 30, 2018 Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number Weighted-Average Exercise Price, Outstanding at December 31, 2017 Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Weighted-Average Exercise Price, Granted Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price Weighted-Average Exercise Price, Exercised Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price Weighted-Average Exercise Price, Expired Share Based Compensation Arrangements By Share Based Payment Award Options Expirations In Period Weighted Average Exercise Price Weighted-Average Exercise Price, Forfeited Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price Weighted-Average Exercise Price, Outstanding at June 30, 2018 Weighted-Average Exercise Price, Options exercisable at June 30, 2018 Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price Excess tax benefits from stock option activity or stock-based compensation expense recognized in cash flows from operations Excess Tax Benefit From Share Based Compensation Operating Activities Pre-tax losses Percentage of the value of the unused research and development tax credits that are allowed to be exchanged for cash by qualified small companies conducting research and development in Connecticut under the Connecticut Research and Development Tax Credit Exchange Program. Percentage of annual research and development credit for cash Percentage Of Research And Development Tax Credits Exchanged For Cash Income tax rate Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate Operating leases future minimum payments due in six years. Schedule Of Operating Leased Assets [Table] Schedule Of Operating Leased Assets [Table] Lease Arrangement, Type Lease Arrangement Type [Axis] Lease Arrangement, Type Lease Arrangement Type [Domain] Stamford operating lease. Stamford Operating Lease [Member] Stamford Operating Lease [Member] Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] 2018 Operating Leases Future Minimum Payments Remainder Of Fiscal Year 2019 Operating Leases Future Minimum Payments Due In Two Years 2020 Operating Leases Future Minimum Payments Due In Three Years 2021 Operating Leases Future Minimum Payments Due In Four Years 2022 Operating Leases Future Minimum Payments Due In Five Years 2023 Operating Leases Future Minimum Payments Due In Six Years Total Operating Leases Future Minimum Payments Due Other Commitments [Table] Other Commitments [Table] Property, Plant and Equipment, Type Property Plant And Equipment By Type [Axis] Property, Plant and Equipment, Type Property Plant And Equipment Type [Domain] Leasehold Improvements [Member] Leasehold Improvements [Member] Credit Facility Credit Facility [Axis] Credit Facility Credit Facility [Domain] Standby Letter of Credit [Member] Standby Letters Of Credit [Member] Other Commitments [Line Items] Other Commitments [Line Items] Operating Lease, description Description Of Lessee Leasing Arrangements Operating Leases Operating Lease, renewable term Lessee Operating Lease Renewal Term Operating lease, expiration date Lease Expiration Date1 Tenant improvement expenses Tenant Improvements Lease Renewal Date Lessee Leasing Arrangements Operating Leases Renewal Term Description Letter of credit, amount Line Of Credit Facility Maximum Borrowing Capacity Letter of credit, renewal date Lease Renewal Date Operating lease, renewable term description Lessee Leasing Arrangements Operating Leases Renewal Term Description Consulting services period of services. Subsequent Event [Table] Subsequent Event [Table] Former CMO. Former CMO [Member] Former C M O [Member] Subsequent Event Type Subsequent Event Type [Axis] Subsequent Event Type Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Consulting services, period of services Consulting Services Period Of Services