Loans and Allowance for Loan Losses - Table of loan payment estimates - (Details 3) - USD ($)	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jul. 26, 2013	Dec. 31, 2012
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Allowance for loan losses on acquired loans	$ 0
First Financial Holdings, Inc. ("First Financial")
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest				$ 900,439,000
Non-accretable difference				(121,974,000)
Cash flows expected to be collected				778,465,000
Accretable difference				(181,956,000)
Total acquired loans				596,509,000
Acquired non-credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Total acquired loans	1,049,538,000	$ 1,327,999,000
Acquired non-credit impaired loans | First Financial Holdings, Inc. ("First Financial")
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest				238,166,000
Non-accretable difference				(11,905,000)
Cash flows expected to be collected				226,261,000
Accretable difference				(52,122,000)
Total acquired loans				174,139,000
Acquired credit impaired loans
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest	968,857,000	1,337,703,000
Non-accretable difference	(29,743,000)	(104,110,000)
Cash flows expected to be collected	939,114,000	1,233,593,000
Accretable difference	(201,538,000)	(306,826,000)
Total acquired loans	737,576,000	926,767,000	$ 1,232,256,000
Allowance for loan losses on acquired loans	$ (3,706,000)	$ (7,365,000)	$ (11,618,000)		$ (17,218,000)
Acquired credit impaired loans | First Financial Holdings, Inc. ("First Financial")
Contractual loan payments receivable, estimates of amounts not expected to be collected, other fair value adjustments and the resulting fair values of acquired loans
Contractual principal and interest				662,273,000
Non-accretable difference				(110,069,000)
Cash flows expected to be collected				552,204,000
Accretable difference				(129,834,000)
Total acquired loans				$ 422,370,000