Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Statement of Stockholders' Equity [Abstract]
Total shareholders’ equity at beginning of period	$ 2,514,161	$ 2,417,482
Net income	205,273	175,295
Other comprehensive income (loss)	14,842	(92,321)
Stock option exercises (491,675 shares in 2014 and 1,249,874 shares in 2013)	25,573	65,026
Stock compensation expense recognized in earnings	6,938	7,310
Tax benefits (deficiencies) related to stock compensation	2,286	1,854
Common stock issued in acquisition of WNB Bancshares (2,000,000 shares)	149,720	0
Issuance of preferred stock (6,000,000 shares in 2013)	0	144,486
Purchase of treasury stock (2,236,748 shares in 2013)	0	(144,000)
Cash dividends – preferred stock (approximately $1.01 per share in 2014 and $0.78 per share in 2013)	(6,047)	(4,703)
Cash dividends – common stock ($1.52 per share in 2014 and $1.48 per share in 2013)	(94,894)	(89,261)
Total shareholders’ equity at end of period	$ 2,817,852	$ 2,481,168