Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Treasury Stock	Additional Paid-in Capital 2025 Notes	Additional Paid-in Capital 2027 Notes	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income	2025 Notes	2027 Notes	Total
Balance at the beginning 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 income (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
Increase (Decrease) in Stockholders' Equity
Net income (loss)						(8,391)				(8,391)
Other comprehensive income (loss), net of tax							(48)			(48)
Share-based compensation expense					12,703					12,703
Net issuance under employee stock plans	$ 7				549					556
Net issuance under employee stock plans (in shares)	730
Extinguishment of equity component of repurchased/exchanged 2023 Notes					(14,714)					(14,714)
Equity component of Notes			$ 20,706	$ 33,363				$ 20,706	$ 33,363
Purchase of capped calls					(10,313)					(10,313)
Balance at the end of the period at Dec. 31, 2020	$ 497				1,113,352	(707,321)	1,846			408,374
Balance (in shares) at Dec. 31, 2020	49,724
Increase (Decrease) in Stockholders' Equity
Net income (loss)						26,038				26,038
Other comprehensive income (loss), net of tax							(363)			(363)
Share-based compensation expense					15,249					15,249
Net issuance under employee stock plans	$ 10				(5,600)					(5,590)
Net issuance under employee stock plans (in shares)	929
Extinguishment of equity component of repurchased/exchanged 2023 Notes					(6,080)					(6,080)
Balance at the end of the period at Dec. 31, 2021	$ 507				$ 1,116,921	$ (681,283)	$ 1,483			$ 437,628
Balance (in shares) at Dec. 31, 2021	50,653