Consolidated Statement of Changes in Equity Statement - USD ($) $ in Thousands	Total	Conversion of Class B Common Stock to Class A Common Stock [Member]	Common Stock [Member] Class A Common Shares [Member]	Common Stock [Member] Class A Common Shares [Member] Conversion of Class B Common Stock to Class A Common Stock [Member]	Common Stock [Member] Class B Common Shares [Member]	Common Stock [Member] Class B Common Shares [Member] Conversion of Class B Common Stock to Class A Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] ASU 2018-02 [Member]	AOCL Attributable to Parent [Member]	AOCL Attributable to Parent [Member] ASU 2018-02 [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]
Stockholders' Equity, balance at Dec. 31, 2016	$ 3,187,121		$ 742		$ 8		$ 1,709,615	$ 1,685,813		$ (197,316)		$ (232,348)	$ 220,607
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income Attributable to Parent	122,485							122,485
Net Income Attributable to Noncontrolling Interest	6,317												6,317
Net income	128,802
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	80,197									80,197
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest													18,346
Other Comprehensive Income (Loss), Net of Tax	98,543
Conversion of Class B Common Stock to Class A Common Stock		$ 0		$ 1		$ 1
Value of stock issued for stock-based compensation	8,003		2				8,001
Settlement of Deferred Stock Awards	738						738
Compensation cost related to stock-based compensation	13,309						13,309
Value of treasury stock repurchased	(3,275)											(3,275)
Other	438						444						(6)
Stockholders' Equity, balance at Sep. 30, 2017	3,433,679		745		7		1,732,107	1,808,298		(117,119)		(235,623)	245,264
Stockholders' Equity, balance at Dec. 31, 2017	3,896,092		748		7		1,757,332	2,234,864		(105,534)		(236,951)	245,626
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income Attributable to Parent	188,856							188,856
Net Income Attributable to Noncontrolling Interest	8,090												8,090
Net income	196,946
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(26,572)									(26,572)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest													(17,585)
Other Comprehensive Income (Loss), Net of Tax	(44,157)
Conversion of Class B Common Stock to Class A Common Stock		$ 0		$ 2		$ 2
Value of stock issued for stock-based compensation	7,814		2				7,812
Settlement of Deferred Stock Awards	995						995
Compensation cost related to stock-based compensation	13,029						13,029
Value of treasury stock repurchased	(273,294)											(273,294)
Distribution to noncontrolling interest	(14,898)												(14,898)
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCL to Retained Earnings	0									(2,970)
United States Tax Cuts and Jobs Act 2017, Reclassification from AOCL to Retained Earnings | Adjustments for New Accounting Principle, Early Adoption [Member]									$ 2,970		$ (2,970)
Other	43												43
Stockholders' Equity, balance at Sep. 30, 2018	$ 3,782,570		$ 752		$ 5		$ 1,779,168	$ 2,426,690		$ (135,076)		$ (510,245)	$ 221,276