Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated Deficit	Cumulative Effect, Period of Adoption, Adjustment	Total
Stockholders' Equity, Beginning Balance (ASU 2016-01) at Dec. 31, 2017			$ 120		$ (120)
Stockholders' Equity, Beginning Balance (ASU 2014-09) at Dec. 31, 2017					$ (19,930)		$ (19,930)
Stockholders' Equity, Beginning Balance at Dec. 31, 2017	$ 32	$ 295,019		$ (287)		$ (160,713)		$ 134,051
Shares, Outstanding, Beginning Balance at Dec. 31, 2017	31,572,044
Exercises of vested stock options		3,891						3,891
Exercises of vested stock options (in shares)	384,186
Vesting of restricted stock units		9						9
Vesting of restricted stock units (in shares)	319,891
Issuance of common stock under ESPP		969						969
Issuance of common stock under ESPP (in shares)	88,774
Stock based compensation expense		15,710						15,710
Unrealized gain (loss) on available for-sale securities, net of tax				34				34
Net (loss) income						(88,288)		(88,288)
Stockholders' Equity, Ending Balance at Dec. 31, 2018	$ 32	315,598		(133)		(269,051)		46,446
Shares, Outstanding, Ending Balance at Dec. 31, 2018	32,364,895
Exercises of vested stock options	$ 1	2,713						2,714
Exercises of vested stock options (in shares)	250,276
Issuance of common stock in connection with Neurocrine Collaboration Agreement	$ 4	77,613						77,617
Issuance of common stock in connection with Neurocrine Collaboration Agreement (in shares)	4,179,728
Issuance of common stock under ESPP		663						663
Issuance of common stock under ESPP (in shares)	70,217
Stock based compensation expense		15,640						15,640
Unrealized gain (loss) on available for-sale securities, net of tax				29				29
Net (loss) income						(43,597)		(43,597)
Stockholders' Equity, Ending Balance at Dec. 31, 2019	$ 37	412,227		(104)		(312,648)		99,512
Shares, Outstanding, Ending Balance at Dec. 31, 2019	36,865,116
Exercises of vested stock options		2,319						$ 2,319
Exercises of vested stock options (in shares)	228,436							228,436
Vesting of restricted stock units (in shares)	170,367
Issuance of common stock under ESPP		1,279						$ 1,279
Issuance of common stock under ESPP (in shares)	104,108
Stock based compensation expense		14,499						14,499
Unrealized gain (loss) on available for-sale securities, net of tax				(30)				(30)
Net (loss) income						36,741		36,741
Stockholders' Equity, Ending Balance at Dec. 31, 2020	$ 37	$ 430,324		$ (134)		$ (275,907)		$ 154,320
Shares, Outstanding, Ending Balance at Dec. 31, 2020	37,368,027