Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Statement of Stockholders' Equity [Abstract]
Total shareholders’ equity at beginning of period	$ 2,514,161	$ 2,417,482
Net income	127,658	114,851
Other comprehensive income (loss)	20,034	(82,446)
Stock option exercises (384,775 shares in 2014 and 662,224 shares in 2013)	20,109	34,189
Stock compensation expense recognized in earnings	4,696	4,985
Tax benefits (deficiencies) related to stock compensation	1,664	(73)
Common stock issued in acquisition of WNB Bancshares (2,000,000 shares)	149,043	0
Issuance of preferred stock (6,000,000 shares in 2013)	0	144,486
Purchase of treasury stock (1,905,077 shares in 2013)	0	(115,200)
Accelerated share repurchase forward contract	0	(28,800)
Cash dividends – preferred stock (approximately $0.67 per share in 2014 and $0.45 per share in 2013)	(4,031)	(2,688)
Cash dividends – common stock ($1.01 per share in 2014 and $0.98 per share in 2013)	(62,660)	(58,948)
Total shareholders’ equity at end of period	$ 2,770,674	$ 2,427,838