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, 2014	$ 2,334,246	$ 144,784	$ 484,155	$ 1,229,075	$ 426,648	$ (16,562)	$ 62,093	$ 4,053
Net income	202,550				200,020			2,530
Other comprehensive income (loss)	3,543						3,543
Distributions to non-controlling interest	(845)							(845)
Purchase of treasury stock	(9,147)					(9,147)
Accelerated stock repurchase agreement	(100,000)			60,000		(160,000)
Issuance of stock under purchase and equity compensation plans	1,914			(15,302)		17,216
Net tax benefit related to equity compensation plans	1,871			1,871
Stock-based compensation	7,702			7,702
Cash dividends per share, Common Stock, Cash	(64,041)				(64,041)
Dividends per share, Preferred Stock, Cash	(6,750)				(6,750)
Balance at Sep. 30, 2015	2,371,043	144,784	484,155	1,283,346	555,877	(168,493)	65,636	5,738
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	204,480				203,812			668
Other comprehensive income (loss)	88,612						88,612
Distributions to non-controlling interest	(704)							(704)
Purchase of treasury stock	(38,476)					(38,476)
Issuance of stock under purchase and equity compensation plans	(3)			(14,057)		14,054
Net tax benefit related to equity compensation plans	2,629			2,629
Stock-based compensation	8,901			8,901
Cash dividends per share, Common Stock, Cash	(65,294)				(65,294)
Dividends per share, Preferred Stock, Cash	(6,750)				(6,750)
Balance at Sep. 30, 2016	$ 2,560,813	$ 144,784	$ 489,862	$ 1,335,150	$ 515,081	$ (50,538)	$ 121,082	$ 5,392