Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative-effect of accounting change adopted as of January 1, 2019	Common stock	APIC	Accumulated Deficit	Accumulated Deficit Cumulative-effect of accounting change adopted as of January 1, 2019
Beginning Balance at Dec. 31, 2018	$ 346,553	$ (3,690)	$ 10	$ 720,025	$ (373,482)	$ (3,690)
Balance (in shares) at Dec. 31, 2018			104,337,508
Increase (Decrease) in Stockholders' Equity
Net loss	(14,365)				(14,365)
Stock-based compensation	9,108			9,108
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes	2,261			2,261
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes (in shares)			781,538
Ending Balance at Mar. 31, 2019	339,867		$ 10	731,394	(391,537)
Balance (in shares) at Mar. 31, 2019			105,119,046
Beginning Balance at Dec. 31, 2018	346,553	$ (3,690)	$ 10	720,025	(373,482)	$ (3,690)
Balance (in shares) at Dec. 31, 2018			104,337,508
Increase (Decrease) in Stockholders' Equity
Net loss	(46,077)
Ending Balance at Sep. 30, 2019	329,978		$ 10	753,217	(423,249)
Balance (in shares) at Sep. 30, 2019			106,492,395
Beginning Balance at Mar. 31, 2019	339,867		$ 10	731,394	(391,537)
Balance (in shares) at Mar. 31, 2019			105,119,046
Increase (Decrease) in Stockholders' Equity
Net loss	(24,060)				(24,060)
Stock-based compensation	16,061			16,061
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes	(469)			(469)
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes (in shares)			776,563
Ending Balance at Jun. 30, 2019	331,399		$ 10	746,986	(415,597)
Balance (in shares) at Jun. 30, 2019			105,895,609
Increase (Decrease) in Stockholders' Equity
Net loss	(7,652)				(7,652)
Stock-based compensation	7,622			7,622
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes	(1,391)			(1,391)
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes (in shares)			596,786
Ending Balance at Sep. 30, 2019	329,978		$ 10	753,217	(423,249)
Balance (in shares) at Sep. 30, 2019			106,492,395
Beginning Balance at Dec. 31, 2019	$ 327,271		$ 11	759,322	(432,062)
Balance (in shares) at Dec. 31, 2019	106,865,830		106,865,830
Increase (Decrease) in Stockholders' Equity
Net loss	$ (10,669)				(10,669)
Stock-based compensation	6,559			6,559
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes	(724)			(724)
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes (in shares)			317,803
Ending Balance at Mar. 31, 2020	322,437		$ 11	765,157	(442,731)
Balance (in shares) at Mar. 31, 2020			107,183,633
Beginning Balance at Dec. 31, 2019	$ 327,271		$ 11	759,322	(432,062)
Balance (in shares) at Dec. 31, 2019	106,865,830		106,865,830
Increase (Decrease) in Stockholders' Equity
Net loss	$ (10,322)
Ending Balance at Sep. 30, 2020	$ 321,903		$ 11	764,276	(442,384)
Balance (in shares) at Sep. 30, 2020	106,072,807		106,072,807
Beginning Balance at Mar. 31, 2020	$ 322,437		$ 11	765,157	(442,731)
Balance (in shares) at Mar. 31, 2020			107,183,633
Increase (Decrease) in Stockholders' Equity
Net loss	(11,242)				(11,242)
Stock-based compensation	6,855			6,855
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes	(856)			(856)
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes (in shares)			726,367
Ending Balance at Jun. 30, 2020	317,194		$ 11	771,156	(453,973)
Balance (in shares) at Jun. 30, 2020			107,910,000
Increase (Decrease) in Stockholders' Equity
Net loss	11,589				11,589
Repurchase of common stock	(11,677)			(11,677)
Repurchase of common stock (in shares)			(2,402,810)
Stock-based compensation	6,217			6,217
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes	(1,420)			(1,420)
Shares issued in connection with employee stock plans, net of shares withheld for employee taxes (in shares)			565,617
Ending Balance at Sep. 30, 2020	$ 321,903		$ 11	$ 764,276	$ (442,384)
Balance (in shares) at Sep. 30, 2020	106,072,807		106,072,807