Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional paid-in capital [Member]	Accumulated other comprehensive income (loss) [Member]	Retained earnings [Member]	Convertible Debt
Beginning Balance at Dec. 31, 2017	$ 227,104	$ 35	$ 239,489	$ 0	$ (12,420)
Beginning Balance, shares at Dec. 31, 2017		34,540,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under equity compensation plans	17,047	$ 0	17,047
Issuance of common stock under equity compensation plans, shares		1,237,000
Stock-based compensation expense	10,078		10,078
Repurchases of common stock	(4,344)	$ 0	(4,344)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	0
Repurchase of common stock, shares		(90,000)
Changes in cumulative translation adjustment, net of tax	(139)			(139)
Issuance of shares in exchange for Convertible Senior Notes	200,219	$ 4	200,215
Number of shares of common stock issued						3,699,000
Tax impact from the conversion of Convertible Senior Notes	2,162		2,162
Reduction for equity component of Convertible Senior Notes exchanged	(100,726)		(100,726)
Net income	74,183				74,183
Ending Balance at Dec. 31, 2018	425,584	$ 39	363,921	(139)	61,763
Ending Balance, shares at Dec. 31, 2018		39,386,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under equity compensation plans	16,799	$ 2	16,797
Issuance of common stock under equity compensation plans, shares		1,152,000
Stock-based compensation expense	12,088		12,088
Repurchases of common stock	(10,728)	$ 0	(10,728)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(324)			(324)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	(2)
Repurchase of common stock, shares		(167,000)
Changes in cumulative translation adjustment, net of tax	(322)
Issuance of shares in exchange for Convertible Senior Notes	86,428	$ 1	86,427
Number of shares of common stock issued						1,497,000
Tax impact from the conversion of Convertible Senior Notes	568		568
Reduction for equity component of Convertible Senior Notes exchanged	(43,516)		(43,516)
Net income	72,921				72,921
Ending Balance at Dec. 31, 2019	559,820	$ 42	425,557	(463)	134,684
Ending Balance, shares at Dec. 31, 2019		41,868,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under equity compensation plans	10,380	$ 0	10,380
Issuance of common stock under equity compensation plans, shares		490,000
Stock-based compensation expense	18,969		18,969
Repurchases of common stock	(47,889)	$ 0	(47,889)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	32			32
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	$ (2,522)
Repurchase of common stock, shares	(257,329)	(294,000)
Changes in cumulative translation adjustment, net of tax	$ 2,554
Issuance of shares in exchange for Convertible Senior Notes	7,230	$ 0	7,230
Number of shares of common stock issued						225,955
Tax impact from the conversion of Convertible Senior Notes	54		54
Reduction for equity component of Convertible Senior Notes exchanged	26,180
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments			26,180
Net income	810,287				810,287
Ending Balance at Dec. 31, 2020	$ 1,332,703	$ 42	$ 388,121	$ (431)	$ 944,971
Ending Balance, shares at Dec. 31, 2020		42,290,000