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
Stockholders' Equity [Roll Forward]
Cumulative effect adjustment from adoption of ASC Topic | ASC Topic 842 [Member]	$ 0	$ 0	$ 0	$ 0	$ 657	$ 657
Balance at beginning of period at Dec. 31, 2018	91	552,564	(1,326,605)	(79,934)	1,635,751	781,867
Stockholders' Equity [Roll Forward]
Net income	0	0	0	0	43,002	43,002
Other comprehensive (loss) income, net of tax	0	0	0	4,140	0	4,140
Repurchase of Class A common stock (Note 6)	0	0	(825)	0	0	(825)
Exercise of employee stock options/vesting of stock awards	0	(4,335)	2,179	0	0	(2,156)
Stock-based compensation	0	5,041	0	0	0	5,041
Cash dividends	0	0	0	0	(20,531)	(20,531)
Balance at end of period at Mar. 31, 2019	91	553,270	(1,325,251)	(75,794)	1,658,879	811,195
Balance at beginning of period at Dec. 31, 2019	91	557,544	(1,324,826)	(85,292)	1,727,772	875,289
Stockholders' Equity [Roll Forward]
Net income	0	0	0	0	19,730	19,730
Other comprehensive (loss) income, net of tax	0	0	0	(14,997)	0	(14,997)
Repurchase of Class A common stock (Note 6)	0	0	(60,886)	0	0	(60,886)
Exercise of employee stock options/vesting of stock awards	0	(3,083)	1,676	0	0	(1,407)
Stock-based compensation	0	3,455	0	0	0	3,455
Cash dividends	0	0	0	0	(20,686)	(20,686)
Balance at end of period at Mar. 31, 2020	$ 91	$ 557,916	$ (1,384,036)	$ (100,289)	$ 1,726,816	$ 800,498