CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance (in shares) at Dec. 31, 2018			81,996,839
Balance at beginning at Dec. 31, 2018	$ 1,075,518		$ 0	$ 1,139,462	$ 0	$ (11,021)	$ (52,923)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercises of employee stock options (in shares)			399,320
Issuance of common stock upon exercises of employee stock options	8,276			8,276
Issuance of common stock upon vesting of RSUs (in shares)			1,510,144
Issuance of common stock for employee stock purchase plan (in shares)			288,529
Issuance of common stock for employee stock purchase plan	7,537			7,537
Stock-based compensation (inclusive of capitalized stock-based compensation)	97,810			97,810
Shares withheld related to net share settlement of equity awards	(33,037)			(33,037)
Repurchases of common stock	(474,993)				(474,993)
Retirement of common stock (in shares)			(13,994,909)
Retirement of common stock					474,993		(474,993)
Foreign currency adjustments	(2,276)					(2,276)
Net (loss) income	23,729						23,729
Balance (in shares) at Sep. 30, 2019			70,199,923
Balance at end at Sep. 30, 2019	702,564		$ 0	1,220,048	0	(13,297)	(504,187)
Balance (in shares) at Jun. 30, 2019			71,931,789
Balance at beginning at Jun. 30, 2019	746,455		$ 0	1,194,486	(5,952)	(11,163)	(430,916)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercises of employee stock options (in shares)			225,364
Issuance of common stock upon exercises of employee stock options	4,615			4,615
Issuance of common stock upon vesting of RSUs (in shares)			527,233
Stock-based compensation (inclusive of capitalized stock-based compensation)	31,140			31,140
Shares withheld related to net share settlement of equity awards	(10,193)			(10,193)
Repurchases of common stock	(77,380)				(77,380)
Retirement of common stock (in shares)			(2,484,463)
Retirement of common stock					83,332		(83,332)
Foreign currency adjustments	(2,134)					(2,134)
Net (loss) income	10,061						10,061
Balance (in shares) at Sep. 30, 2019			70,199,923
Balance at end at Sep. 30, 2019	$ 702,564		$ 0	1,220,048	0	(13,297)	(504,187)
Balance (in shares) at Dec. 31, 2019	71,185,468		71,185,468
Balance at beginning at Dec. 31, 2019	$ 754,991	$ (34)	$ 0	1,259,803	0	(11,759)	(493,053)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercises of employee stock options (in shares)	285,388		285,388
Issuance of common stock upon exercises of employee stock options	$ 3,606			3,606
Issuance of common stock upon vesting of RSUs (in shares)			2,071,934
Issuance of common stock for employee stock purchase plan (in shares)			433,697
Issuance of common stock for employee stock purchase plan	8,014			8,014
Stock-based compensation (inclusive of capitalized stock-based compensation)	99,133			99,133
Shares withheld related to net share settlement of equity awards	(11,752)			(11,752)
Foreign currency adjustments	2,183					2,183
Net (loss) income	$ (40,513)						(40,513)
Balance (in shares) at Sep. 30, 2020	73,976,487		73,976,487
Balance at end at Sep. 30, 2020	$ 815,628		$ 0	1,358,804	0	(9,576)	(533,600)
Balance (in shares) at Jun. 30, 2020			73,121,229
Balance at beginning at Jun. 30, 2020	781,320		$ 0	1,325,745	0	(11,845)	(532,580)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercises of employee stock options (in shares)			63,031
Issuance of common stock upon exercises of employee stock options	812			812
Issuance of common stock upon vesting of RSUs (in shares)			792,227
Stock-based compensation (inclusive of capitalized stock-based compensation)	32,247			32,247
Foreign currency adjustments	2,269					2,269
Net (loss) income	$ (1,020)						(1,020)
Balance (in shares) at Sep. 30, 2020	73,976,487		73,976,487
Balance at end at Sep. 30, 2020	$ 815,628		$ 0	$ 1,358,804	$ 0	$ (9,576)	$ (533,600)