Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Stockholders' Equity, Beginning Balance at Dec. 31, 2018	$ 32	$ 315,598	$ (133)	$ (269,051)	$ 46,446
Shares, Outstanding, Beginning Balance at Dec. 31, 2018	32,364,895
Exercises of vested stock options	$ 1	283			284
Exercises of vested stock options (in shares)	31,360
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
Stock based compensation expense		3,459			3,459
Unrealized gain (loss) on available for-sale securities, net of tax			58		58
Net (loss) income				(27,170)	(27,170)
Stockholders' Equity, Ending Balance at Mar. 31, 2019	$ 37	396,953	(75)	(296,221)	100,694
Shares, Outstanding, Ending Balance at Mar. 31, 2019	36,575,983
Stockholders' Equity, Beginning Balance at Dec. 31, 2018	$ 32	315,598	(133)	(269,051)	46,446
Shares, Outstanding, Beginning Balance at Dec. 31, 2018	32,364,895
Unrealized gain (loss) on available for-sale securities, net of tax					234
Net (loss) income					(16,017)
Stockholders' Equity, Ending Balance at Jun. 30, 2019	$ 37	403,334	101	(285,068)	118,404
Shares, Outstanding, Ending Balance at Jun. 30, 2019	36,677,608
Stockholders' Equity, Beginning Balance at Mar. 31, 2019	$ 37	396,953	(75)	(296,221)	100,694
Shares, Outstanding, Beginning Balance at Mar. 31, 2019	36,575,983
Exercises of vested stock options		714			714
Exercises of vested stock options (in shares)	57,461
Issuance of common stock under ESPP		471			471
Issuance of common stock under ESPP (in shares)	44,164
Stock based compensation expense		5,196			5,196
Unrealized gain (loss) on available for-sale securities, net of tax			176		176
Net (loss) income				11,153	11,153
Stockholders' Equity, Ending Balance at Jun. 30, 2019	$ 37	403,334	101	(285,068)	118,404
Shares, Outstanding, Ending Balance at Jun. 30, 2019	36,677,608
Stockholders' Equity, Beginning Balance at Dec. 31, 2019	$ 37	412,227	(104)	(312,648)	99,512
Shares, Outstanding, Beginning Balance at Dec. 31, 2019	36,865,116
Vesting of restricted stock units (in shares)	108,600
Exercises of vested stock options		34			34
Exercises of vested stock options (in shares)	3,035
Stock based compensation expense		3,949			3,949
Unrealized gain (loss) on available for-sale securities, net of tax			525		525
Net (loss) income				(24,263)	(24,263)
Stockholders' Equity, Ending Balance at Mar. 31, 2020	$ 37	416,210	421	(336,911)	79,757
Shares, Outstanding, Ending Balance at Mar. 31, 2020	36,976,751
Stockholders' Equity, Beginning Balance at Dec. 31, 2019	$ 37	412,227	(104)	(312,648)	$ 99,512
Shares, Outstanding, Beginning Balance at Dec. 31, 2019	36,865,116
Exercises of vested stock options (in shares)					163,513
Unrealized gain (loss) on available for-sale securities, net of tax					$ 249
Net (loss) income					(32,944)
Stockholders' Equity, Ending Balance at Jun. 30, 2020	$ 37	422,294	145	(345,592)	76,884
Shares, Outstanding, Ending Balance at Jun. 30, 2020	37,203,627
Stockholders' Equity, Beginning Balance at Mar. 31, 2020	$ 37	416,210	421	(336,911)	79,757
Shares, Outstanding, Beginning Balance at Mar. 31, 2020	36,976,751
Vesting of restricted stock units (in shares)	21,403
Exercises of vested stock options		1,651			1,651
Exercises of vested stock options (in shares)	160,478
Issuance of common stock under ESPP		638			638
Issuance of common stock under ESPP (in shares)	44,995
Stock based compensation expense		3,795			3,795
Unrealized gain (loss) on available for-sale securities, net of tax			(276)		(276)
Net (loss) income				(8,681)	(8,681)
Stockholders' Equity, Ending Balance at Jun. 30, 2020	$ 37	$ 422,294	$ 145	$ (345,592)	$ 76,884
Shares, Outstanding, Ending Balance at Jun. 30, 2020	37,203,627