Consolidated Statement of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Stockholders' Equity, Beginning Balance at Dec. 31, 2018	$ 486,365	$ 27	$ 633,251	$ (223)	$ (146,690)
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2018		26,922,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	574		574
Shares issued under employee stock plans (in shares)		84,000
Stock-based compensation	2,867		2,867
Comprehensive income (loss), net	427			427
Net loss	(22,078)				(22,078)
Stockholders' Equity, Ending Balance at Mar. 31, 2019	468,155	$ 27	636,692	204	(168,768)
Stockholders' Equity, Ending Balance (in shares) at Mar. 31, 2019		27,006,000
Stockholders' Equity, Beginning Balance at Dec. 31, 2018	486,365	$ 27	633,251	(223)	(146,690)
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2018		26,922,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(77,073)
Stockholders' Equity, Ending Balance at Sep. 30, 2019	420,892	$ 27	644,148	480	(223,763)
Stockholders' Equity, Ending Balance (in shares) at Sep. 30, 2019		27,098,000
Stockholders' Equity, Beginning Balance at Mar. 31, 2019	468,155	$ 27	636,692	204	(168,768)
Stockholders' Equity, Beginning Balance (in shares) at Mar. 31, 2019		27,006,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	215		215
Shares issued under employee stock plans (in shares)		39,000
Stock-based compensation	3,643		3,643
Comprehensive income (loss), net	370			370
Net loss	(23,962)				(23,962)
Stockholders' Equity, Ending Balance at Jun. 30, 2019	448,421	$ 27	640,550	574	(192,730)
Stockholders' Equity, Ending Balance (in shares) at Jun. 30, 2019		27,045,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	454		454
Shares issued under employee stock plans (in shares)		53,000
Stock-based compensation	3,144		3,144
Comprehensive income (loss), net	(94)			(94)
Net loss	(31,033)				(31,033)
Stockholders' Equity, Ending Balance at Sep. 30, 2019	420,892	$ 27	644,148	480	(223,763)
Stockholders' Equity, Ending Balance (in shares) at Sep. 30, 2019		27,098,000
Stockholders' Equity, Beginning Balance at Dec. 31, 2019	405,008	$ 27	648,669	338	(244,026)
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2019		27,255,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	36		36
Shares issued under employee stock plans (in shares)		22,000
Stock-based compensation	2,975		2,975
Comprehensive income (loss), net	807			807
Net loss	(8,262)				(8,262)
Stockholders' Equity, Ending Balance at Mar. 31, 2020	400,564	$ 27	651,680	1,145	(252,288)
Stockholders' Equity, Ending Balance (in shares) at Mar. 31, 2020		27,277,000
Stockholders' Equity, Beginning Balance at Dec. 31, 2019	$ 405,008	$ 27	648,669	338	(244,026)
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2019		27,255,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans (in shares)	91,146
Net loss	$ (53,577)
Stockholders' Equity, Ending Balance at Sep. 30, 2020	360,243	$ 27	657,560	259	(297,603)
Stockholders' Equity, Ending Balance (in shares) at Sep. 30, 2020		27,346,000
Stockholders' Equity, Beginning Balance at Mar. 31, 2020	400,564	$ 27	651,680	1,145	(252,288)
Stockholders' Equity, Beginning Balance (in shares) at Mar. 31, 2020		27,277,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	71		71
Shares issued under employee stock plans (in shares)		10,000
Stock-based compensation	2,741		2,741
Comprehensive income (loss), net	(392)			(392)
Net loss	(21,548)				(21,548)
Stockholders' Equity, Ending Balance at Jun. 30, 2020	381,436	$ 27	654,492	753	(273,836)
Stockholders' Equity, Ending Balance (in shares) at Jun. 30, 2020		27,287,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	263		263
Shares issued under employee stock plans (in shares)		59,000
Stock-based compensation	2,805		2,805
Comprehensive income (loss), net	(494)			(494)
Net loss	(23,767)				(23,767)
Stockholders' Equity, Ending Balance at Sep. 30, 2020	$ 360,243	$ 27	$ 657,560	$ 259	$ (297,603)
Stockholders' Equity, Ending Balance (in shares) at Sep. 30, 2020		27,346,000