Consolidated Statements Of Changes In Equity (USD $) In Thousands	Total	Preferred Stock [Member]	Common Stock	Capital Surplus	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Non-Controlling Interest
Balance at Dec. 31, 2011	$ 2,170,361	$ 0	$ 446,387	$ 1,042,065	$ 575,419	$ (8,362)	$ 110,538	$ 4,314
Net income	271,439				269,329			2,110
Other comprehensive income	25,806						25,806
Distributions to non-controlling interest	(1,977)							(1,977)
Purchase of treasury stock	(104,909)					(104,909)
Cash dividends paid on common stock	(211,608)				(211,608)
Net tax benefit related to equity compensation plans	2,094			2,094
Stock-based compensation	5,001			5,001
Issuance under stock purchase and equity compensation plans, net	15,588			(16,905)		32,493
5% stock dividend, net	(221)		12,259	70,252	(155,930)	73,198
Balance at Dec. 31, 2012	2,171,574	0	458,646	1,102,507	477,210	(7,580)	136,344	4,447
Net income	261,117				260,961			156
Other comprehensive income	(126,613)						(126,613)
Acquisition of Summit Bancshares, Inc.	43,197		1,001	11,125		31,071
Distributions to non-controlling interest	(848)							(848)
Purchase of treasury stock	(69,353)					(69,353)
Cash dividends paid on common stock	(82,104)				(82,104)
Net tax benefit related to equity compensation plans	1,003			1,003
Stock-based compensation	6,427			6,427
Issuance under stock purchase and equity compensation plans, net	10,242			(14,824)		25,066
5% stock dividend, net	(245)		21,577	173,710	(206,231)	10,699
Balance at Dec. 31, 2013	2,214,397	0	481,224	1,279,948	449,836	(10,097)	9,731	3,755
Net income	262,784				261,754			1,030
Other comprehensive income	52,362						52,362
Distributions to non-controlling interest	(732)							(732)
Issuance of preferred stock	144,784	144,784
Purchase of treasury stock	(210,974)					(210,974)
Accelerated share repurchase forward contract	(60,000)			(60,000)
Cash dividends paid on common stock	(84,241)				(84,241)
Cash dividends paid on preferred stock	(4,050)				(4,050)
Net tax benefit related to equity compensation plans	1,850			1,850
Stock-based compensation	8,829			8,829
Issuance under stock purchase and equity compensation plans, net	9,506			(14,703)		24,209
5% stock dividend, net	(269)		2,931	13,151	(196,651)	180,300
Balance at Dec. 31, 2014	$ 2,334,246	$ 144,784	$ 484,155	$ 1,229,075	$ 426,648	$ (16,562)	$ 62,093	$ 4,053