Organization, Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Adjustment of Carrying Value to Their Estimated Fair Value (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)	May 07, 2019 USD ($)
Takeda and Lender Warrants
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of warrant liabilities	$ 107,373	$ 47,894
Takeda Warrants
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of warrant liabilities	$ 107,000
Takeda Warrants | Income Approach | Discount Rate
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities, measurement input	7.5
Takeda Warrants | Minimum | Financing Transactions
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities, measurement input	9.33
Warrant liabilities, measurement input [Extensible List]	us-gaap:MeasurementInputExercisePriceMember
Takeda Warrants | Minimum | Income Approach | Expected Term
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities, term	1 month 2 days
Takeda Warrants | Maximum | Financing Transactions
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities, measurement input	18.56
Warrant liabilities, measurement input [Extensible List]	us-gaap:MeasurementInputExercisePriceMember
Takeda Warrants | Maximum | Income Approach | Expected Term
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities, term	1 year 9 months 7 days
May 2019 Notes
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of convertible promissory notes	$ 95,229	$ 90,250
May 2019 Notes | Income Approach | Volatility
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible promissory notes, measurement input	65
May 2019 Notes | Minimum | Financing Transactions
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible promissory notes, term	1 month 2 days
Convertible promissory notes, measurement input [Extensible List]	us-gaap:MeasurementInputExpectedTermMember
May 2019 Notes | Minimum | Income Approach | Discount Rate
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible promissory notes, measurement input	22.6
May 2019 Notes | Maximum | Financing Transactions
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible promissory notes, term	1 year 9 months 7 days
Convertible promissory notes, measurement input [Extensible List]	us-gaap:MeasurementInputExpectedTermMember
May 2019 Notes | Maximum | Income Approach | Discount Rate
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible promissory notes, measurement input	25