CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	2025 Convertible Notes	2022 Convertible Notes	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital 2025 Convertible Notes	Additional Paid-in Capital 2022 Convertible Notes	Accumulated Deficit	Treasury Stock
Balance at Dec. 31, 2018	$ 346,208			$ 154	$ 1,134,227			$ (610,482)	$ (177,691)
Balance (in shares) at Dec. 31, 2018				15,428,000					2,618,000
Increase (Decrease) in Stockholders' Equity
Net income (loss) and comprehensive income (loss)	17,828							17,828
Non-cash compensation	52,167				52,167
Purchase of treasury stock	$ (5,470)								$ (5,470)
Purchase of treasury stock (in shares)	22,731								23,000
Issuance of common stock for stock options, employee stock purchase plan, restricted stock awards and restricted stock units, net of withholding taxes	$ (8,406)			$ 3	(8,409)
Issuance of common stock for stock options, employee stock purchase plan, restricted stock awards and restricted stock units, net of withholding taxes (in shares)				249,000
Other	(1)				(1)
Balance at Dec. 31, 2019	402,326			$ 157	1,177,984			(592,654)	$ (183,161)
Balance (in shares) at Dec. 31, 2019				15,677,000					2,641,000
Increase (Decrease) in Stockholders' Equity
Net income (loss) and comprehensive income (loss)	(48,255)							(48,255)
Non-cash compensation	53,733				53,733
Issuance of common stock for stock options, employee stock purchase plan, restricted stock awards and restricted stock units, net of withholding taxes	(3,910)			$ 1	(3,911)
Issuance of common stock for stock options, employee stock purchase plan, restricted stock awards and restricted stock units, net of withholding taxes (in shares)				89,000
Issuance of 0.50% Convertible Senior Notes, net		$ 116,300				$ 116,300
Repurchase of 0.625% Convertible Senior Notes, net			$ (107,882)				$ (107,882)
Convertible note hedge transactions	(14,379)				(14,379)
Warrant transactions	(33,171)				(33,171)
Other	(1)				(1)
Balance at Dec. 31, 2020	364,761			$ 158	1,188,673			(640,909)	$ (183,161)
Balance (in shares) at Dec. 31, 2020				15,766,000					2,641,000
Increase (Decrease) in Stockholders' Equity
Net income (loss) and comprehensive income (loss)	69,115							69,115
Non-cash compensation	68,555				68,555
Purchase of treasury stock	$ (40,008)								$ (40,008)
Purchase of treasury stock (in shares)	334,253								335,000
Issuance of common stock for stock options, employee stock purchase plan, restricted stock awards and restricted stock units, net of withholding taxes	$ (14,423)			$ 3	(14,426)
Issuance of common stock for stock options, employee stock purchase plan, restricted stock awards and restricted stock units, net of withholding taxes (in shares)				305,000
Other	(8)				(8)
Balance at Dec. 31, 2021	$ 447,992			$ 161	$ 1,242,794			$ (571,794)	$ (223,169)
Balance (in shares) at Dec. 31, 2021				16,071,000					2,976,000