Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Common Stock [Member] Common Class A [Member]	Common Stock [Member] Common Class B [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock, Common [Member]	Retained Earnings [Member] Common Class A [Member]	Retained Earnings [Member] Common Class B [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Parent [Member] Common Class A [Member]	Parent [Member] Common Class B [Member]	Parent [Member]	Noncontrolling Interest [Member]	Common Class A [Member]	Common Class B [Member]	Total
Balance (in shares) at Dec. 31, 2020	63,756,000	18,705,000
Balance at Dec. 31, 2020			$ 551	$ 437,646	$ (2,879)			$ 831,850	$ 869			$ 1,268,037				$ 1,268,037
Stock options exercised and stock awards (in shares)	1,176,000
Stock options exercised and stock awards			8	14,157								14,165				14,165
Stock-based compensation related to stock options, restricted shares and employee stock purchase plan				22,246								22,246				22,246
Vesting of restricted share awards		$ 520	3	(7,447)								(7,444)				(7,444)
Issuance of common stock under employee stock purchase plan (in shares)	224,000
Issuance of common stock under employee stock purchase plan			1	4,148								4,149				4,149
Common stock repurchases (in shares)	(494,000)	(627,000)
Common stock repurchases					(34,054)							(34,054)				(34,054)
Cash dividends declared on common stock						$ (31,816)	$ (9,867)			$ (31,816)	$ (9,867)			$ (31,816)	$ (9,867)
Other comprehensive income									(82)			(82)				(82)
Net income								241,415				241,415				241,415
Foreign currency translation adjustment																(82)
Foreign currency translation																(82)
Balance (in shares) at Dec. 31, 2021	64,662,000	18,598,000
Balance at Dec. 31, 2021			563	470,750	(36,933)			1,031,582	787			1,466,749				1,466,749
Stock options exercised and stock awards (in shares)	585
Stock options exercised and stock awards			4	8,029								8,033				8,033
Stock-based compensation related to stock options, restricted shares and employee stock purchase plan				25,315								25,315				25,315
Vesting of restricted share awards			3	(8,669)								(8,666)				(8,666)
Issuance of common stock under employee stock purchase plan (in shares)	201,000
Issuance of common stock under employee stock purchase plan			2	5,217								5,219				5,219
Common stock repurchases (in shares)	(1,930,000)	(930,000)
Common stock repurchases					(93,997)							(93,997)				(93,997)
Cash dividends declared on common stock						(34,207)	(10,420)			(34,207)	(10,420)			(34,207)	(10,420)
Net income								391,382				391,382	$ 703			392,085
Vesting of restricted share awards (in shares)		457
Reclassification of foreign currency translation related to equity method									(601)			(601)				(601)
Foreign currency translation adjustment									(4,316)			(4,316)				(4,316)
Foreign currency translation									(4,316)			(4,316)				(4,316)
Noncontrolling interest equity													17,828			17,828
Balance (in shares) at Dec. 31, 2022	63,518,000	18,125,000
Balance at Dec. 31, 2022			572	500,642	(130,930)			1,378,337	(4,130)			1,744,491				$ 1,763,022
Stock options exercised and stock awards (in shares)	822															800,988
Stock options exercised and stock awards			6	12,120								12,126				$ 12,126
Stock-based compensation related to stock options, restricted shares and employee stock purchase plan				30,354								30,354				30,354
Vesting of restricted share awards			3	(7,018)								(7,015)				(7,015)
Issuance of common stock under employee stock purchase plan (in shares)	209,000
Issuance of common stock under employee stock purchase plan												5,952				5,952
Common stock repurchases (in shares)	(3,088)	(2,182)
Common stock repurchases					(213,425)							(213,425)				(213,425)
Cash dividends declared on common stock						$ (38,727)	$ (11,896)			$ (38,727)	$ (11,896)			$ (38,727)	$ (11,896)
Net income								347,055				347,055	1,006			348,061
Vesting of restricted share awards (in shares)		421,000
Foreign currency translation adjustment									1,967			1,967				1,967
Foreign currency translation									1,967			1,967				1,967
Retirement of treasury shares and par value adjustment			224	(3)	224,520			(224,744)				(3)				(3)
Balance (in shares) at Dec. 31, 2023	61,461,000	16,364,000
Balance at Dec. 31, 2023			$ 806	$ 542,046	$ (119,835)			$ 1,450,025	$ (2,163)			$ 1,870,879	$ 19,537			$ 1,890,416