Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member] Class A [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Total
Balance at beginning of period at Dec. 31, 2020	$ 91	$ 579,801	$ (1,461,593)	$ (64,768)	$ 1,840,740	$ 894,271
Stockholders' Equity [Roll Forward]
Net income	0	0	0	0	106,768	106,768
Other comprehensive income (loss), net of tax	0	0	0	(3,785)	0	(3,785)
Repurchase of Class A common stock (Note 6)	0	0	(60,410)	0	0	(60,410)
Exercise of employee stock options/vesting of stock awards	0	(6,208)	12,136	0	0	5,928
Stock-based compensation	0	13,383	0	0	0	13,383
Cash dividends	0	0	0	0	(38,329)	(38,329)
Balance at end of period at Jun. 30, 2021	91	586,976	(1,509,867)	(68,553)	1,909,179	917,826
Balance at beginning of period at Mar. 31, 2021	91	579,204	(1,505,076)	(71,626)	1,868,881	871,474
Stockholders' Equity [Roll Forward]
Net income	0	0	0	0	59,338	59,338
Other comprehensive income (loss), net of tax	0	0	0	3,073	0	3,073
Repurchase of Class A common stock (Note 6)	0	0	(10,004)	0	0	(10,004)
Exercise of employee stock options/vesting of stock awards	0	1,192	5,213	0	0	6,405
Stock-based compensation	0	6,580	0	0	0	6,580
Cash dividends	0	0	0	0	(19,040)	(19,040)
Balance at end of period at Jun. 30, 2021	91	586,976	(1,509,867)	(68,553)	1,909,179	917,826
Balance at beginning of period at Dec. 31, 2021	91	601,703	(1,526,860)	(73,896)	1,911,734	912,772
Stockholders' Equity [Roll Forward]
Net income	0	0	0	0	72,953	72,953
Other comprehensive income (loss), net of tax	0	0	0	(16,742)	0	(16,742)
Repurchase of Class A common stock (Note 6)	0	0	(20,010)	0	0	(20,010)
Exercise of employee stock options/vesting of stock awards	0	(1,503)	26,101	0	0	24,598
Stock-based compensation	0	6,149	0	0	0	6,149
Cash dividends	0	0	0	0	(38,685)	(38,685)
Balance at end of period at Jun. 30, 2022	91	606,349	(1,520,769)	(90,638)	1,946,002	941,035
Balance at beginning of period at Mar. 31, 2022	91	599,258	(1,526,778)	(69,528)	1,931,157	934,200
Stockholders' Equity [Roll Forward]
Net income	0	0	0	0	34,237	34,237
Other comprehensive income (loss), net of tax	0	0	0	(21,110)	0	(21,110)
Repurchase of Class A common stock (Note 6)	0	0	(10,004)	0	0	(10,004)
Exercise of employee stock options/vesting of stock awards	0	5,069	16,013	0	0	21,082
Stock-based compensation	0	2,022	0	0	0	2,022
Cash dividends	0	0	0	0	(19,392)	(19,392)
Balance at end of period at Jun. 30, 2022	$ 91	$ 606,349	$ (1,520,769)	$ (90,638)	$ 1,946,002	$ 941,035