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Debt (Details)	1 Months Ended	12 Months Ended
Debt (Details)	Apr. 30, 2020 USD ($) D	Dec. 31, 2020 USD ($) D $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($)	Sep. 30, 2020 shares	Oct. 31, 2019 $ / shares shares	Apr. 30, 2019 $ / shares shares	Jul. 31, 2018 $ / shares shares	Aug. 31, 2017 USD ($) shares	Aug. 08, 2017 USD ($)	Sep. 30, 2015 USD ($)
Debt Instrument [Line Items]
Proceeds from Convertible Note, net of issuance costs		$ 278,316,000
Common Stock, Par or Stated Value Per Share \| $ / shares		$ 0.0001	$ 0.0001
Issuance of common stock to Orbimed			$ 507,000
Common stock, shares issued \| shares		86,223,000	78,005,000		4,791,665	5,714,286	5,263,158	4,500,000
Stock issued (in dollars per share) \| $ / shares						$ 35	$ 19	$ 20
Equity component	$ 85,600,000
Debt, repayment amount		$ 79,200,000
Accrued Interest		1,078,000
Amortization of debt discount and issuance cost		149,000	$ 457,000	$ 391,000
Interest expense		15,082,000	10,693,000	10,476,000
Convertible Notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 287,500,000	287,500,000
Per annum interest rate (as a percent)	2.25%
Interest expense		11,630,000
Unamortized debt discount		$ 8,625,000
Debt instrument, term		7 years
Effective interest rate (as a percent)		8.27%
Principal amount per convertible note	$ 1,000
Threshold business days \| D	5
Conversion price (in dollars per share) \| $ / shares		$ 38.79
Initial conversion rate		25.7785
Convertible to shares of common stock		7,411,704
Percentage of principal amount converted		100.00%
Carrying value		$ 202,493,000
Equity component	$ 85,600,000
Debt Instrument, debt discount, Equity Component		79,100,000
Debt Instrument, debt discount, Liability Component		5,600,000
Debt issuance costs		$ 558,000
Commencing after September 30, 2020 \| Convertible Notes
Debt Instrument [Line Items]
Threshold trading days \| D	30
Percentage of conversion price	130.00%
5 consecutive trading day period \| Convertible Notes
Debt Instrument [Line Items]
Threshold trading days \| D	5
Percentage of conversion price	98.00%
Redeemable for cash on or after May 2024 \| Convertible Notes
Debt Instrument [Line Items]
Threshold trading days \| D		30
Percentage of conversion price		130.00%
Percentage of principal amount converted		100.00%
Debt Component \| Convertible Notes
Debt Instrument [Line Items]
Unamortized debt discount		$ 6,057,000
Debt issuance costs		$ 392,000
Measurement input, risk free interest rate
Debt Instrument [Line Items]
Debt Instrument, Measurement Input	7.832
Level 2
Debt Instrument [Line Items]
Fair value of liability	$ 201,900,000
Minimum \| Commencing after September 30, 2020 \| Convertible Notes
Debt Instrument [Line Items]
Threshold trading days \| D	20
Minimum \| Redeemable for cash on or after May 2024 \| Convertible Notes
Debt Instrument [Line Items]
Threshold trading days \| D		20
Line Of Credit-UBS
Debt Instrument [Line Items]
Maximum borrowing capacity											$ 50,000,000.0
Outstanding balance		$ 49,000,000.0
Interest expense		800,000	1,700,000	1,600,000
Interest paid		800,000	1,700,000	$ 1,500,000
Debt, interest accrued		$ 1,100,000
Line Of Credit-UBS \| LIBOR
Debt Instrument [Line Items]
Spread on interest rate (as a percent)		1.10%
2017 Term Loan
Debt Instrument [Line Items]
Maximum borrowing capacity										$ 100,000,000.0
Outstanding balance										75,000,000.0
Remaining borrowing capacity			50,000,000.0						$ 50,000,000.0	$ 25,000,000.0
Interest expense		$ 2,500,000	$ 9,000,000.0
Unamortized debt discount		$ 2,091,000
Common stock, shares issued \| shares			25,000				25,000		300,000
Debt, repayment amount	$ 79,200,000
Accrued Interest	$ 400,000
2017 Term Loan \| Minimum
Debt Instrument [Line Items]
Remaining borrowing capacity			$ 25,000,000.0
2017 Term Loan \| LIBOR
Debt Instrument [Line Items]
Spread on interest rate (as a percent)			8.75%
Base interest rate (as a percent)			1.00%
2017 Term Loan \| LIBOR \| Minimum borrowing capacity drawn
Debt Instrument [Line Items]
Spread on interest rate (as a percent)			8.25%
Base interest rate (as a percent)			1.00%
2017 Term Loan \| Noncurrent assets
Debt Instrument [Line Items]
Debt instrument, fee amount									$ 1,200,000