Business Combinations - Statement of Assets Purchased and Liabilities Assumed (Details) - USD ($) $ in Thousands	Feb. 15, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Total Assets			$ 0	$ 1,845,543
Liabilities
Total Liabilities			0	1,821,066
Goodwill		$ 366,156	$ 365,500	$ 372,851
BancTrust Financial Group, Inc. [Member]
Assets
Cash and due from banks	$ 141,616
Securities available for sale	528,016
Loans held for sale	1,050
Acquired noncovered loans	944,235
Premises and equipment, net	54,952
Identifiable intangible assets	33,498
Other real estate	40,103
Other assets	109,423
Total Assets	1,852,893
Liabilities
Deposits	1,740,254
Other borrowings	64,051
Other liabilities	16,761
Total Liabilities	1,821,066
Net identified assets acquired at fair value	31,827
Goodwill	74,247
Net assets acquired at fair value	$ 106,074