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, Common	Noncontrolling Interest [Member]	Class A Common Stock [Member] Common Stock [Member]	Class B Common Stock [Member] Common Stock [Member]
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 Stockholders' Equity [Roll Forward]
Net income for the year	353,327		353,327
Noncontrolling interest capital contribution	3,350					3,350
Net income attributable to noncontrolling interest	0		(1,943)			1,943
Acquisition of redeemable noncontrolling interest	0
Net Loss (Income) Attributable to Redeemable Noncontrolling Interest	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 (loss), 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
As of at Dec. 31, 2020	11,928
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the year	70,434		70,434
Noncontrolling interest capital contribution	3,900					3,900
Acquisition of noncontrolling interest	512					512
Sale of equity in subsidiary	3,200	146				3,054
Net income attributable to noncontrolling interest	0		(3,384)			3,384
Acquisition of redeemable noncontrolling interest	0
Net Loss (Income) Attributable to Redeemable Noncontrolling Interest	29		29
Change in redemption value of redeemable noncontrolling interests	(5,780)	(6,027)				247
Distribution to noncontrolling interest	(1,905)					(1,905)
Dividends paid on common stock	(30,712)		(30,712)
Repurchase of Class B common stock	(71,386)				(71,386)
Issuance of Class B common stock, net of restricted stock award forfeitures	341	(733)			1,074
Amortization of unearned stock compensation and stock option expense	7,596	7,596
Other comprehensive income (loss), net of income taxes	(635,237)			(635,237)
Purchase of redeemable noncontrolling interest	0
As of at Dec. 31, 2022	3,752,661	390,438	7,163,128	336,151	(4,178,334)	21,278	964	19,036
Increase (Decrease) in Temporary Equity [Roll Forward]
Noncontrolling interest capital contributions	1,050
Acquisition of redeemable noncontrolling interest	2,164
Net income (loss) attributable to redeemable noncontrolling interests	(29)
Change in redemption value of redeemable noncontrolling interests	6,281
Distribution to noncontrolling interests	(750)
Purchase of redeemable noncontrolling interest	(1,200)
As of at Dec. 31, 2022	21,827
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the year	211,704		211,704
Noncontrolling interest capital contribution	3,520					3,520
Purchase of equity from noncontrolling interest	(4,988)	(5,742)				754
Net income attributable to noncontrolling interest	0		(3,512)			3,512
Net Loss (Income) Attributable to Redeemable Noncontrolling Interest	(2,904)		(2,904)
Change in redemption value of redeemable noncontrolling interests	(14,923)	(15,441)				518
Distribution to noncontrolling interest	(3,451)					(3,451)
Dividends paid on common stock	(30,953)		(30,953)
Repurchase of Class B common stock	(195,002)				(195,002)
Issuance of Class B common stock, net of restricted stock award forfeitures	1,123	(4,110)			5,233
Amortization of unearned stock compensation and stock option expense	6,895	6,895
Other comprehensive income (loss), net of income taxes	278,186			278,186
Purchase of redeemable noncontrolling interest	0
As of at Dec. 31, 2023	4,001,868	$ 372,040	$ 7,337,463	$ 614,337	$ (4,368,103)	$ 26,131	$ 964	$ 19,036
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (loss) attributable to redeemable noncontrolling interests	2,904
Change in redemption value of redeemable noncontrolling interests	15,660
Distribution to noncontrolling interests	(1,241)
Purchase of redeemable noncontrolling interest	(14,965)
As of at Dec. 31, 2023	$ 24,185