Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Total
Balance at the beginning of the period at Dec. 31, 2016	$ 407	$ (2,309)	$ 763,303	$ (161,474)	$ 1,777	$ 601,704
Balance (in shares) at Dec. 31, 2016	40,715	127
Increase (Decrease) in Stockholders' Equity
Net loss				(51,396)		(51,396)
Other comprehensive income (loss), net of tax					35	35
Share-based compensation expense			24,396			24,396
Net issuance under employee stock plans	$ 3	$ 4,043	(9,795)			(5,749)
Net issuance under employee stock plans (in shares)	313	(245)
Stock issuance for business acquisition	$ 72		228,800			228,872
Stock issuance for business acquisition (in shares)	7,201
Convertible Senior Notes, equity component			45,249			45,249
Purchases of common stock		$ (3,018)				(3,018)
Purchase of common stock (in shares)		203
Balance at the end of the period at Dec. 31, 2017	$ 482	$ (1,284)	1,051,953	(212,870)	1,812	840,093
Balance (in shares) at Dec. 31, 2017	48,229	85
Increase (Decrease) in Stockholders' Equity
Net loss				(407,088)		(407,088)
Other comprehensive income (loss), net of tax					8	8
Share-based compensation expense			16,074			16,074
Net issuance under employee stock plans	$ 3	$ 6,721	(6,702)	(25)		(3)
Net issuance under employee stock plans (in shares)	318	(512)
Purchases of common stock		$ (11,309)				(11,309)
Purchase of common stock (in shares)		950
Balance at the end of the period at Dec. 31, 2018	$ 485	$ (5,872)	1,061,325	(619,983)	1,820	437,775
Balance (in shares) at Dec. 31, 2018	48,547	523
Increase (Decrease) in Stockholders' Equity
Net loss				(78,733)		(78,733)
Other comprehensive income (loss), net of tax					74	74
Share-based compensation expense			15,270			15,270
Net issuance under employee stock plans	$ 5	$ 5,872	(5,537)	(214)		126
Net issuance under employee stock plans (in shares)	447	(523)
Balance at the end of the period at Dec. 31, 2019	$ 490		$ 1,071,058	$ (698,930)	$ 1,894	$ 374,512
Balance (in shares) at Dec. 31, 2019	48,994