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	47,430	47,430
Other comprehensive income (loss), net of tax	0	0	0	(6,858)	0	(6,858)
Repurchase of Class A common stock (Note 6)	0	0	(50,406)	0	0	(50,406)
Exercise of employee stock options/vesting of stock awards	0	(7,400)	6,923	0	0	(477)
Stock-based compensation	0	6,803	0	0	0	6,803
Cash dividends	0	0	0	0	(19,289)	(19,289)
Balance at end of period at Mar. 31, 2021	91	579,204	(1,505,076)	(71,626)	1,868,881	871,474
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	38,716	38,716
Other comprehensive income (loss), net of tax	0	0	0	4,368	0	4,368
Repurchase of Class A common stock (Note 6)	0	0	(10,006)	0	0	(10,006)
Exercise of employee stock options/vesting of stock awards	0	(6,572)	10,088	0	0	3,516
Stock-based compensation	0	4,127	0	0	0	4,127
Cash dividends	0	0	0	0	(19,293)	(19,293)
Balance at end of period at Mar. 31, 2022	$ 91	$ 599,258	$ (1,526,778)	$ (69,528)	$ 1,931,157	$ 934,200