Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Gain (Loss)	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Retained Earnings (Accumulated Deficit)
Beginning balance (in shares) at Dec. 31, 2018		61,579
Beginning Balance at Dec. 31, 2018	$ 301,818	$ 6	$ 315,291	$ (12,908)	$ (571)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Receipt of Section 16(b) disgorgement, net of tax effect	3,743		3,743
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units (in shares)		863
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units	8,587		8,587
Stock-based compensation	5,335		5,335
Equity settled contingent consideration (in shares)		21
Equity-settled contingent consideration	750		750
Cumulative translation adjustment	(1,011)				(1,011)
Unrealized gain (loss) on investments, net of tax	702				702
Net income (loss)	5,914			5,914
Ending balance (in shares) at Mar. 31, 2019		62,463
Ending Balance at Mar. 31, 2019	325,838	$ 6	333,706	(6,994)	(880)
Beginning balance (in shares) at Dec. 31, 2018		61,579
Beginning Balance at Dec. 31, 2018	301,818	$ 6	315,291	(12,908)	(571)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative translation adjustment	49
Unrealized gain (loss) on investments, net of tax	912
Net income (loss)	(3,545)
Ending balance (in shares) at Sep. 30, 2019		65,047
Ending Balance at Sep. 30, 2019	386,735	$ 7	402,791	(16,453)	390
Beginning balance (in shares) at Dec. 31, 2018		61,579
Beginning Balance at Dec. 31, 2018	301,818	$ 6	315,291	(12,908)	(571)
Ending balance (in shares) at Dec. 31, 2019		65,260
Ending Balance at Dec. 31, 2019	$ 424,907	$ 7	412,191	14,235	(1,526)	$ (609)	$ (609)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Beginning balance (in shares) at Mar. 31, 2019		62,463
Beginning Balance at Mar. 31, 2019	$ 325,838	$ 6	333,706	(6,994)	(880)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units (in shares)		309
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units	(620)		(620)
Stock-based compensation	8,024		8,024
Cumulative translation adjustment	1,193				1,193
Unrealized gain (loss) on investments, net of tax	212				212
Net income (loss)	(3,219)			(3,219)
Ending balance (in shares) at Jun. 30, 2019		62,772
Ending Balance at Jun. 30, 2019	331,428	$ 6	341,110	(10,213)	525
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units (in shares)		370
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units	3,703		3,703
Induced conversion on 2023 Notes, net of tax (in shares)		2,190
Induced conversion on 2023 Notes, net of tax	(7,904)	$ 1	(7,905)
Extinguishment of capped calls (in shares)		(285)
Extinguishment of capped calls
Stock-based compensation	8,836		8,836
Equity component of 2024 & 2026 Notes, net of issuance costs and tax	122,822		122,822
Purchase of capped calls, net of tax	(65,775)		(65,775)
Cumulative translation adjustment	(133)				(133)
Unrealized gain (loss) on investments, net of tax	(2)				(2)
Net income (loss)	(6,240)			(6,240)
Ending balance (in shares) at Sep. 30, 2019		65,047
Ending Balance at Sep. 30, 2019	386,735	$ 7	402,791	(16,453)	390
Beginning balance (in shares) at Dec. 31, 2019		65,260
Beginning Balance at Dec. 31, 2019	424,907	$ 7	412,191	14,235	(1,526)	(609)	(609)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units (in shares)		625
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units	1,655		1,655
Stock-based compensation	13,664		13,664
Cumulative translation adjustment	998				998
Unrealized gain (loss) on investments, net of tax	1,243				1,243
Net income (loss)	(15,473)			(15,473)
Ending balance (in shares) at Mar. 31, 2020		65,885
Ending Balance at Mar. 31, 2020	426,385	$ 7	427,510	(1,847)	715
Beginning balance (in shares) at Dec. 31, 2019		65,260
Beginning Balance at Dec. 31, 2019	424,907	$ 7	412,191	14,235	(1,526)	$ (609)	$ (609)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative translation adjustment	361
Unrealized gain (loss) on investments, net of tax	1,750
Net income (loss)	(46,409)
Ending balance (in shares) at Sep. 30, 2020		66,543
Ending Balance at Sep. 30, 2020	$ 435,890	$ 7	468,081	(32,783)	585
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Beginning balance (in shares) at Mar. 31, 2020		65,885
Beginning Balance at Mar. 31, 2020	$ 426,385	$ 7	427,510	(1,847)	715
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units (in shares)		259
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units	(967)		(967)
Stock-based compensation	16,923		16,923
Cumulative translation adjustment	613				613
Unrealized gain (loss) on investments, net of tax	1,817				1,817
Net income (loss)	(35,293)			(35,293)
Ending balance (in shares) at Jun. 30, 2020		66,144
Ending Balance at Jun. 30, 2020	409,478	$ 7	443,466	(37,140)	3,145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units (in shares)		399
Shares issued pursuant to stock awards, net of tax withholdings related to vesting of restricted stock units	3,919		3,919
Induced conversion on 2023 Notes, net of tax	(1)		(1)
Stock-based compensation	20,697		20,697
Cumulative translation adjustment	(1,250)				(1,250)
Unrealized gain (loss) on investments, net of tax	(1,310)				(1,310)
Net income (loss)	4,357			4,357
Ending balance (in shares) at Sep. 30, 2020		66,543
Ending Balance at Sep. 30, 2020	$ 435,890	$ 7	$ 468,081	$ (32,783)	$ 585