Consolidated Statements Of Changes In Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-Controlling Interest [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-09 [Member]	$ 1,297			$ 3,441	$ (2,144)
Balance at Dec. 31, 2016	2,501,132	$ 144,784	$ 510,015	1,552,454	292,849	$ (15,294)	$ 10,975	$ 5,349
Net income	224,917				225,028			(111)
Other comprehensive income (loss)	56,086						56,086
Distributions to non-controlling interest	(1,305)							(1,305)
Purchase of treasury stock	(11,320)					(11,320)
Issuance of stock under purchase and equity compensation plans	(7)			(16,726)		16,719
Stock-based compensation	9,149			9,149
Cash dividends per share, Common Stock, Cash	(68,722)				(68,722)
Dividends per share, Preferred Stock, Cash	(6,750)				(6,750)
Balance at Sep. 30, 2017	2,704,477	144,784	510,015	1,548,318	440,261	(9,895)	67,061	3,933
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2018-02 [Member]	0				(2,932)		2,932
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01 [Member]	0				33,320		(33,320)
Balance at Dec. 31, 2017	2,718,184	144,784	535,407	1,815,360	221,374	(14,473)	14,108	1,624
Net income	327,454				323,890			3,564
Other comprehensive income (loss)	(125,316)						(125,316)
Distributions to non-controlling interest	(471)							(471)
Purchase of treasury stock	(39,575)					(39,575)
Issuance of stock under purchase and equity compensation plans	(10)			(20,884)		20,874
Stock-based compensation	9,555			9,555
Cash dividends per share, Common Stock, Cash	(75,261)				(75,261)
Dividends per share, Preferred Stock, Cash	(6,750)				(6,750)
Balance at Sep. 30, 2018	$ 2,807,810	$ 144,784	$ 535,407	$ 1,804,031	$ 493,641	$ (33,174)	$ (141,596)	$ 4,717