Loan Servicing, Mortgage Origination, and Loans Held for Sale (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
MSRs
Changes in the fair value of MSRs and its offsetting hedge
Gains (losses) related to derivatives	$ 1,720	$ 183	$ 2,150	$ 2,118
Characteristics and sensitivity analysis of the MSR
Composition of residential loans serviced for others	100.00%	100.00%	100.00%	100.00%	100.00%
Weighted average life			6 years 9 months 15 days	6 years 2 months 19 days	6 years 3 months 18 days
Constant prepayment rate (as a percent)			10.20%	11.50%	11.40%
Weighted average discount rate (as a percent)			9.80%	9.50%	9.70%
Effect on fair value due to change in interest rates:
25 basis point increase	$ 1,555	$ 1,499	$ 1,555	$ 1,499	$ 1,365
50 basis point increase	2,945	2,803	2,945	2,803	2,555
25 basis point decrease	(1,883)	(1,688)	(1,883)	(1,688)	(1,562)
50 basis point decrease	(3,964)	(3,229)	(3,964)	(3,229)	$ (3,221)
Custodial escrow balances maintained in connection with the loan servicing	$ 21,400	$ 18,600	$ 21,400	$ 18,600
Fixed-rate mortgage loans
Characteristics and sensitivity analysis of the MSR
Composition of residential loans serviced for others	99.40%	99.20%	99.40%	99.20%	99.20%
Adjustable-rate mortgage loans
Characteristics and sensitivity analysis of the MSR
Composition of residential loans serviced for others	0.60%	0.80%	0.60%	0.80%	0.80%
First Financial Holdings, Inc. ("First Financial")
Loans held for sale, loan servicing and mortgage origination
Residential mortgages serviced for others	$ 2,500,000	$ 2,200,000	$ 2,500,000	$ 2,200,000	$ 2,300,000
Contractually specified servicing fees earned	$ 1,600	$ 1,200	$ 4,700	$ 3,900