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	71,702				71,504			198
Other comprehensive income (loss)	19,437						19,437
Distributions to non-controlling interest	(685)							(685)
Purchase of treasury stock	(7,284)					(7,284)
Issuance of stock under purchase and equity compensation plans	(6)			(14,996)		14,990
Stock-based compensation	3,135			3,135
Cash dividends per share, Common Stock, Cash	(22,913)				(22,913)
Dividends per share, Preferred Stock, Cash	(2,250)				(2,250)
Balance at Mar. 31, 2017	2,563,565	144,784	510,015	1,544,034	337,046	(7,588)	30,412	4,862
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	102,061				100,984			1,077
Other comprehensive income (loss)	(73,283)						(73,283)
Distributions to non-controlling interest	(95)							(95)
Purchase of treasury stock	(17,067)					(17,067)
Issuance of stock under purchase and equity compensation plans	(6)			(15,865)		15,859
Stock-based compensation	3,290			3,290
Cash dividends per share, Common Stock, Cash	(25,106)				(25,106)
Dividends per share, Preferred Stock, Cash	(2,250)				(2,250)
Balance at Mar. 31, 2018	$ 2,705,728	$ 144,784	$ 535,407	$ 1,802,785	$ 325,390	$ (15,681)	$ (89,563)	$ 2,606