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	150,691				150,464			227
Other comprehensive income (loss)	31,095						31,095
Distributions to non-controlling interest	(1,252)							(1,252)
Purchase of treasury stock	(10,628)					(10,628)
Issuance of stock under purchase and equity compensation plans	(7)			(15,556)		15,549
Stock-based compensation	6,195			6,195
Cash dividends per share, Common Stock, Cash	(45,816)				(45,816)
Dividends per share, Preferred Stock, Cash	(4,500)				(4,500)
Balance at Jun. 30, 2017	2,628,207	144,784	510,015	1,546,534	390,853	(10,373)	42,070	4,324
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	213,385				211,314			2,071
Other comprehensive income (loss)	(92,501)						(92,501)
Distributions to non-controlling interest	(299)							(299)
Purchase of treasury stock	(19,069)					(19,069)
Issuance of stock under purchase and equity compensation plans	(9)			(17,697)		17,688
Stock-based compensation	6,394			6,394
Cash dividends per share, Common Stock, Cash	(50,202)				(50,202)
Dividends per share, Preferred Stock, Cash	(4,500)				(4,500)
Balance at Jun. 30, 2018	$ 2,771,383	$ 144,784	$ 535,407	$ 1,804,057	$ 408,374	$ (15,854)	$ (108,781)	$ 3,396