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 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
Balance at Dec. 31, 2018	2,937,149	144,784	559,432	2,084,824	241,163	(34,236)	(64,669)	5,851
Net income	97,055				97,138			(83)
Other comprehensive income (loss)	76,650						76,650
Distributions to non-controlling interest	(310)							(310)
Purchase of treasury stock	(39,699)					(39,699)
Issuance of stock under purchase and equity compensation plans	(4)			(13,392)		13,388
Stock-based compensation	3,480			3,480
Cash dividends per share, Common Stock, Cash	(28,858)				(28,858)
Dividends per share, Preferred Stock, Cash	(2,250)				(2,250)
Balance at Mar. 31, 2019	$ 3,043,213	$ 144,784	$ 559,432	$ 2,074,912	$ 307,193	$ (60,547)	$ 11,981	$ 5,458