Business Combinations, (BancTrust Financial Group, Pro forma Financial Information (Details) (BancTrust Financial Group, Inc. [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
BancTrust Financial Group, Inc. [Member]
Unaudited pro forma financial information [Abstract]
Net Interest Income	$ 96,514	$ 102,872
Total Noninterest Income	46,202	47,634
Net income	$ 32,675	$ 34,531
Pro Forma Earnings Per Common Share [Abstract]
Basic (in dollars per share)	$ 0.49	$ 0.52
Diluted (in dollars per share)	$ 0.49	$ 0.52