Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital	Retained Earnings (Deficit)	Accumulated Other Comprehensive Income (Loss)
Balance (in shares) at Dec. 31, 2019		40,074,000
Balance at Dec. 31, 2019	$ 410,180	$ 40	$ 485,239	$ (64,740)	$ (10,359)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	30,912	0	0	30,912	0
Foreign currency translation	(5,430)	0	0	0	(5,430)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	2,837
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	(8,510)	$ 0	0	0	(8,510)
Repurchases of common stock, net of retirements (shares)		(362,000)
Repurchases of common stock, net of retirements	(66,619)	$ 0	0	(66,619)	0
Share-based compensation	3,654	$ 0	3,654	0	0
Issuance of shares under share-based compensation plans (shares)		219,000
Issuance of stock under share-based compensation plans	6,358	$ 0	6,358	0	0
Declaration of cash dividends	(22,147)	$ 0	0	(22,147)	0
Balance (in shares) at Mar. 31, 2020		39,931,000
Balance at Mar. 31, 2020	348,398	$ 40	495,251	(122,594)	(24,299)
Balance (in shares) at Dec. 31, 2019		40,074,000
Balance at Dec. 31, 2019	410,180	$ 40	485,239	(64,740)	(10,359)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	307,565
Foreign currency translation	(320)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	3,641
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	$ (10,923)
Balance (in shares) at Sep. 30, 2020	40,153,287	40,153,000
Balance at Sep. 30, 2020	$ 589,501	$ 40	513,030	98,033	(21,602)
Balance (in shares) at Mar. 31, 2020		39,931,000
Balance at Mar. 31, 2020	348,398	$ 40	495,251	(122,594)	(24,299)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	157,555	0	0	157,555	0
Foreign currency translation	2,134	0	0	0	2,134
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	855
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	(2,567)	$ 0	0	0	(2,567)
Repurchases of common stock, net of retirements (shares)		(19,000)
Repurchases of common stock, net of retirements	(3,584)	$ 0	0	(3,584)	0
Share-based compensation	3,567	$ 0	3,567	0	0
Issuance of shares under share-based compensation plans (shares)		130,000
Issuance of stock under share-based compensation plans	4,453	$ 0	4,453	0	0
Declaration of cash dividends	(23,165)	$ 0	0	(23,165)	0
Balance (in shares) at Jun. 30, 2020		40,042,000
Balance at Jun. 30, 2020	486,791	$ 40	503,271	8,212	(24,732)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	119,098	0	0	119,098	0
Foreign currency translation	2,976	0	0	0	2,976
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	(51)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	154	$ 0	0	0	154
Repurchases of common stock, net of retirements (shares)		(20,000)
Repurchases of common stock, net of retirements	(5,990)	$ 0	0	(5,990)	0
Share-based compensation	3,874	$ 0	3,874	0	0
Issuance of shares under share-based compensation plans (shares)		131,000
Issuance of stock under share-based compensation plans	5,885	$ 0	5,885	0	0
Declaration of cash dividends	$ (23,287)	$ 0	0	(23,287)	0
Balance (in shares) at Sep. 30, 2020	40,153,287	40,153,000
Balance at Sep. 30, 2020	$ 589,501	$ 40	513,030	98,033	(21,602)
Balance (in shares) at Dec. 31, 2020	40,232,210	40,232,000
Balance at Dec. 31, 2020	$ 639,470	$ 40	519,579	133,870	(14,019)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	98,655	0	0	98,655	0
Foreign currency translation	(1,268)	0	0	0	(1,268)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	(3,046)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	9,137	$ 0	0	0	9,137
Repurchases of common stock, net of retirements (shares)		(215,000)
Repurchases of common stock, net of retirements	(71,516)	$ 0	0	(71,516)	0
Share-based compensation	3,837	$ 0	3,837	0	0
Issuance of shares under share-based compensation plans (shares)		69,000
Issuance of stock under share-based compensation plans	2,912	$ 0	2,912	0	0
Declaration of cash dividends	(23,299)	$ 0	0	(23,299)	0
Balance (in shares) at Mar. 31, 2021		40,086,000
Balance at Mar. 31, 2021	$ 657,928	$ 40	526,328	137,710	(6,150)
Balance (in shares) at Dec. 31, 2020	40,232,210	40,232,000
Balance at Dec. 31, 2020	$ 639,470	$ 40	519,579	133,870	(14,019)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	543,015
Foreign currency translation	(3,522)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	(2,818)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	$ 8,453
Balance (in shares) at Sep. 30, 2021	40,079,584	40,080,000
Balance at Sep. 30, 2021	$ 985,212	$ 40	542,858	451,401	(9,087)
Balance (in shares) at Mar. 31, 2021		40,086,000
Balance at Mar. 31, 2021	657,928	$ 40	526,328	137,710	(6,150)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	259,695	0	0	259,695	0
Foreign currency translation	1,302	0	0	0	1,302
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	719
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	(2,157)	$ 0	0	0	(2,157)
Repurchases of common stock, net of retirements (shares)		(45,000)
Repurchases of common stock, net of retirements	(18,619)	$ 0	0	(18,619)	0
Share-based compensation	3,712	$ 0	3,712	0	0
Issuance of shares under share-based compensation plans (shares)		90,000
Issuance of stock under share-based compensation plans	5,006	$ 0	5,006	0	0
Declaration of cash dividends	(32,119)	$ 0	0	(32,119)	0
Balance (in shares) at Jun. 30, 2021		40,131,000
Balance at Jun. 30, 2021	874,748	$ 40	535,046	346,667	(7,005)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	184,665	0	0	184,665	0
Foreign currency translation	(3,555)	0	0	0	(3,555)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	(491)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	1,473	$ 0	0	0	1,473
Repurchases of common stock, net of retirements (shares)		(100,000)
Repurchases of common stock, net of retirements	(47,840)	$ 0	0	(47,840)	0
Share-based compensation	4,206	$ 0	4,206	0	0
Issuance of shares under share-based compensation plans (shares)		49,000
Issuance of stock under share-based compensation plans	3,606	$ 0	3,606	0	0
Declaration of cash dividends	$ (32,091)	$ 0	0	(32,091)	0
Balance (in shares) at Sep. 30, 2021	40,079,584	40,080,000
Balance at Sep. 30, 2021	$ 985,212	$ 40	$ 542,858	$ 451,401	$ (9,087)