Consolidated Statements of Changes in Common Shareholders' Equity - USD ($) $ in Thousands	Total	Capital in Excess of Par Value [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]	Class A Common Stock [Member] Common Stock [Member]	Class B Common Stock [Member] Common Stock [Member]
As of at Dec. 31, 2018	$ 2,916,782	$ 378,837	$ 6,236,125	$ 203,829	$ (3,922,009)	$ 0	$ 964	$ 19,036
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the year	327,879		327,879
Issuance of noncontrolling interest	6,556					6,556
Acquisition of redeemable noncontrolling interest	0
Net (income) loss attributable to noncontrolling interest	0		152			(152)
Acquisition of noncontrolling interest	1,153					1,153
Net (income) loss attributable to redeemable noncontrolling interests	(176)		(176)
Change in redemption value of redeemable noncontrolling interests	32	32
Dividends paid on common stock	(29,553)		(29,553)
Repurchase of Class B common stock	(2,103)				(2,103)
Issuance of Class B common stock, net of restricted stock award forfeitures	239	(3,721)			3,960
Amortization of unearned stock compensation and stock option expense	6,521	6,521
Other comprehensive income, net of income taxes	99,466			99,466
Purchase of redeemable noncontrolling interest	0
As of at Dec. 31, 2019	3,326,796	381,669	6,534,427	303,295	(3,920,152)	7,557	964	19,036
As of at Dec. 31, 2018	4,346
Increase (Decrease) in Temporary Equity [Roll Forward]
Acquisition of redeemable noncontrolling interest	1,715
Net income (loss) attributable to redeemable noncontrolling interests	176
Change in redemption value of redeemable noncontrolling interests	(32)
Purchase of redeemable noncontrolling interest	(550)
As of at Dec. 31, 2019	5,655
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the year	299,968		299,968
Acquisition of redeemable noncontrolling interest	0
Net (income) loss attributable to noncontrolling interest	0		386			(386)
Net (income) loss attributable to redeemable noncontrolling interests	11		11
Change in redemption value of redeemable noncontrolling interests	273					273
Distribution to noncontrolling interest	(353)					(353)
Dividends paid on common stock	(29,970)		(29,970)
Repurchase of Class B common stock	(161,829)				(161,829)
Issuance of Class B common stock, net of restricted stock award forfeitures	24,577	(411)			24,988
Amortization of unearned stock compensation and stock option expense	6,901	6,901
Other comprehensive income, net of income taxes	300,019			300,019
As of at Dec. 31, 2020	3,766,393	388,159	6,804,822	603,314	(4,056,993)	7,091	964	19,036
Increase (Decrease) in Temporary Equity [Roll Forward]
Acquisition of redeemable noncontrolling interest	6,005
Net income (loss) attributable to redeemable noncontrolling interests	(11)
Change in redemption value of redeemable noncontrolling interests	279
As of at Dec. 31, 2020	11,928
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the year	353,327		353,327
Issuance of noncontrolling interest	3,350					3,350
Acquisition of redeemable noncontrolling interest	0
Net (income) loss attributable to noncontrolling interest	0		(1,943)			1,943
Net (income) loss attributable to redeemable noncontrolling interests	691		691
Change in redemption value of redeemable noncontrolling interests	549	292				257
Distribution to noncontrolling interest	(555)					(555)
Dividends paid on common stock	(30,136)		(30,136)
Repurchase of Class B common stock	(55,683)				(55,683)
Issuance of Class B common stock, net of restricted stock award forfeitures	(939)	(5,593)			4,654
Amortization of unearned stock compensation and stock option expense	6,598	6,598
Other comprehensive income, net of income taxes	368,074			368,074
Purchase of redeemable noncontrolling interest	0
As of at Dec. 31, 2021	4,411,669	$ 389,456	$ 7,126,761	$ 971,388	$ (4,108,022)	$ 12,086	$ 964	$ 19,036
Increase (Decrease) in Temporary Equity [Roll Forward]
Acquisition of redeemable noncontrolling interest	6,617
Net income (loss) attributable to redeemable noncontrolling interests	(691)
Change in redemption value of redeemable noncontrolling interests	(35)
Purchase of redeemable noncontrolling interest	(3,508)
As of at Dec. 31, 2021	$ 14,311