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]
Balance at Dec. 31, 2015	$ 2,367,418	$ 144,784	$ 489,862	$ 1,337,677	$ 383,313	$ (26,116)	$ 32,470	$ 5,428
Net income	135,330				135,267			63
Other comprehensive income (loss)	101,954						101,954
Distributions to non-controlling interest	(586)							(586)
Purchase of treasury stock	(37,462)					(37,462)
Issuance of stock under purchase and equity compensation plans	(2)			(11,873)		11,871
Excess (net) tax benefit related to equity compensation plans	1,904			1,904
Stock-based compensation	6,287			6,287
Cash dividends per share, Common Stock, Cash	(43,522)				(43,522)
Dividends per share, Preferred Stock, Cash	(4,500)				(4,500)
Balance at Jun. 30, 2016	2,526,821	144,784	489,862	1,333,995	470,558	(51,707)	134,424	4,905
Balance at Dec. 31, 2016	2,501,132	144,784	510,015	1,552,454	292,849	(15,294)	10,975	5,349
Adoption of ASU 2016-09	1,297			3,441	(2,144)
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