Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income
Beginning Balance at Dec. 31, 2016	$ 436,541	$ 282	$ 1,310,847	$ (641,869)	$ (219,125)	$ (13,594)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises	21,410	16	21,394
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(15,572)				(15,572)
Employee taxes paid on withholding shares	37,482		37,482
Common stock repurchases	(9,542)				(9,542)
Unrealized loss on available-for-sale securities	26,637					26,637
Unrealized gain on derivatives	1					1
Unrealized gain on derivatives	965					965
Net income	(33,933)			(33,933)
Ending Balance at Dec. 31, 2017	472,898	298	1,375,391	(672,561)	(244,239)	14,009
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect Adjustment Upon the Adoption of ASU	8,909
Cumulative Effect Adjustment Upon the Adoption of ASU | Accounting Standards Update 2016-09			5,668	3,241
Stock option exercises	6,504	12	6,492
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(30,770)				(30,770)
Employee taxes paid on withholding shares	33,799		33,799
Unrealized loss on available-for-sale securities	(7,249)					(7,249)
Unrealized gain on derivatives	0
Unrealized gain on derivatives	10					10
Net income	35,728			35,728
Ending Balance at Dec. 31, 2018	535,768	310	1,415,682	(611,985)	(275,009)	6,770
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect Adjustment Upon the Adoption of ASU	24,848
Cumulative Effect Adjustment Upon the Adoption of ASU | Accounting Standards Update 2014-09				24,848
Stock option exercises	1,981	6	1,975
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(21,034)				(21,034)
Employee taxes paid on withholding shares	45,242		45,242
Common stock repurchases	(10,000)				(10,000)
Unrealized loss on available-for-sale securities	4,535					4,535
Unrealized gain on derivatives	0
Equity component of convertible notes, net of issuance costs and tax	50,123		50,123
Equity component of convertible notes, net of issuance costs and tax	(21,553)		(21,553)
Asset Acquisition, Consideration Transferred By Stock	3,000		3,000
Unrealized gain on derivatives	(1,976)					(1,976)
Net income	(19,482)
Ending Balance at Dec. 31, 2019	567,062	$ 316	$ 1,494,469	(631,009)	$ (306,043)	$ 9,329
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect Adjustment Upon the Adoption of ASU	$ 458
Cumulative Effect Adjustment Upon the Adoption of ASU | Accounting Standards Update 2016-02				$ 458