Condensed Consolidated Statements of Changes in Common Stockholders' Equity Statement - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]
As of at Dec. 31, 2018	$ 2,916,782	$ 20,000	$ 378,837	$ 6,236,125	$ 203,829	$ (3,922,009)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) for the period	81,702			81,702
Issuance of noncontrolling interest	6,000						6,000
Net (income) loss attributable to noncontrolling interest	0			62			(62)
Net income attributable to redeemable noncontrolling interests	(16)			(16)
Change in redemption value of redeemable noncontrolling interest	(54)		(54)
Dividends on common stock	(14,779)			(14,779)
Issuance of Class B common stock, net of restricted stock award forfeitures	(28)		(3,783)			3,755
Amortization of unearned stock compensation and stock option expense	1,639		1,639
Other comprehensive income (loss), net of income taxes	8,290				8,290
Purchase of redeemable noncontrolling interest	0
As of at Mar. 31, 2019	2,999,536	20,000	376,639	6,303,094	212,119	(3,918,254)	5,938
As of at Dec. 31, 2018	4,346
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income attributable to redeemable noncontrolling interests	16
Change in redemption value of redeemable noncontrolling interests	54
Purchase of redeemable noncontrolling interest	(550)
As of at Mar. 31, 2019	3,866
As of at Dec. 31, 2018	2,916,782	20,000	378,837	6,236,125	203,829	(3,922,009)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) for the period	181,862
Other comprehensive income (loss), net of income taxes	(21,891)
As of at Sep. 30, 2019	3,058,911	20,000	379,923	6,388,546	181,938	(3,918,397)	6,901
As of at Dec. 31, 2018	4,346
As of at Sep. 30, 2019	3,903
As of at Mar. 31, 2019	2,999,536	20,000	376,639	6,303,094	212,119	(3,918,254)	5,938
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) for the period	57,195			57,195
Net (income) loss attributable to noncontrolling interest	0			(104)			104
Net income attributable to redeemable noncontrolling interests	(10)			(10)
Dividends on common stock	(7,388)			(7,388)
Amortization of unearned stock compensation and stock option expense	1,616		1,616
Other comprehensive income (loss), net of income taxes	(12,095)				(12,095)
As of at Jun. 30, 2019	3,038,854	20,000	378,255	6,352,787	200,024	(3,918,254)	6,042
As of at Mar. 31, 2019	3,866
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income attributable to redeemable noncontrolling interests	10
As of at Jun. 30, 2019	3,876
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) for the period	42,965			42,965
Issuance of noncontrolling interest	536						536
Net (income) loss attributable to noncontrolling interest	0			207			(207)
Acquisition of noncontrolling interest	530						530
Net income attributable to redeemable noncontrolling interests	(27)			(27)
Dividends on common stock	(7,386)			(7,386)
Issuance of Class B common stock, net of restricted stock award forfeitures	(144)		(1)			(143)
Amortization of unearned stock compensation and stock option expense	1,669		1,669
Other comprehensive income (loss), net of income taxes	(18,086)				(18,086)
As of at Sep. 30, 2019	3,058,911	20,000	379,923	6,388,546	181,938	(3,918,397)	6,901
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income attributable to redeemable noncontrolling interests	27
As of at Sep. 30, 2019	3,903
As of at Dec. 31, 2019	3,326,796	20,000	381,669	6,534,427	303,295	(3,920,152)	7,557
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) for the period	(33,891)			(33,891)
Net (income) loss attributable to noncontrolling interest	0			772			(772)
Net income attributable to redeemable noncontrolling interests	(126)			(126)
Dividends on common stock	(15,289)			(15,289)
Repurchase of Class B Common Stock	(33,610)					(33,610)
Issuance of Class B common stock, net of restricted stock award forfeitures	5,335					5,335
Amortization of unearned stock compensation and stock option expense	1,568		1,568
Other comprehensive income (loss), net of income taxes	(37,943)				(37,943)
As of at Mar. 31, 2020	3,212,840	20,000	383,237	6,485,893	265,352	(3,948,427)	6,785
As of at Dec. 31, 2019	5,655
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income attributable to redeemable noncontrolling interests	126
As of at Mar. 31, 2020	5,781
As of at Dec. 31, 2019	3,326,796	20,000	381,669	6,534,427	303,295	(3,920,152)	7,557
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) for the period	63,025
Other comprehensive income (loss), net of income taxes	388
As of at Sep. 30, 2020	3,246,658	20,000	386,506	6,567,676	303,683	(4,038,052)	6,845
As of at Dec. 31, 2019	5,655
As of at Sep. 30, 2020	11,897
As of at Mar. 31, 2020	3,212,840	20,000	383,237	6,485,893	265,352	(3,948,427)	6,785
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) for the period	18,862			18,862
Net (income) loss attributable to noncontrolling interest	0			37			(37)
Acquisition of redeemable noncontrolling interest	0
Net income attributable to redeemable noncontrolling interests	(45)			(45)
Dividends on common stock	(7,581)			(7,581)
Repurchase of Class B Common Stock	(29,295)					(29,295)
Amortization of unearned stock compensation and stock option expense	1,567		1,567
Other comprehensive income (loss), net of income taxes	17,068				17,068
As of at Jun. 30, 2020	3,213,416	20,000	384,804	6,497,166	282,420	(3,977,722)	6,748
As of at Mar. 31, 2020	5,781
Increase (Decrease) in Temporary Equity [Roll Forward]
Acquisition of redeemable noncontrolling interest	6,005
Net income attributable to redeemable noncontrolling interests	45
As of at Jun. 30, 2020	11,831
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) for the period	78,054			78,054
Net (income) loss attributable to noncontrolling interest	0			(373)			373
Net income attributable to redeemable noncontrolling interests	(66)			(66)
Distribution to noncontrolling interest	(276)						(276)
Dividends on common stock	(7,100)			(7,100)
Repurchase of Class B Common Stock	(60,250)					(60,250)
Issuance of Class B common stock, net of restricted stock award forfeitures	(146)		(66)			(80)
Amortization of unearned stock compensation and stock option expense	1,768		1,768
Other comprehensive income (loss), net of income taxes	21,263				21,263
Other	(5)			(5)
As of at Sep. 30, 2020	3,246,658	$ 20,000	$ 386,506	$ 6,567,676	$ 303,683	$ (4,038,052)	$ 6,845
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income attributable to redeemable noncontrolling interests	66
As of at Sep. 30, 2020	$ 11,897