Mergers and Acquisitions-First Financial Holdings, Inc. Merger- (Details 2)		12 Months Ended
	Jul. 26, 2013 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)
Mergers and Acquisitions
Preferred Stock, Shares Outstanding | shares		0	0
Asset
Bank owned life insurance		$ 101,588,000	$ 99,140,000
Deposits:
Goodwill		338,340,000	317,688,000	$ 317,688,000
Consideration:
Provision for Loan Losses Expensed		5,864,000	6,590,000	1,886,000
Other Real Estate, Valuation Adjustments		9,428,000	10,685,000	8,109,000
Proforma amounts
Total revenues (net interest income plus noninterest income), Pro Forma		443,328,000	421,056,000	438,625,000
Net operating income available to the common shareholder, Pro Forma		104,391,000	$ 90,573,000	80,624,000
First Financial Holdings, Inc. ("First Financial")
Mergers and Acquisitions
Business Acquisition Equity Interests Issued or Issuable Number of Shares Issued Exchange Ratio	0.4237
Common shares issued | shares	7,018,274
Preferred Stock, Value, Outstanding	$ 65,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 530,000
Preferred Stock, Shares Outstanding | shares	65,000
Preferred Stock, Liquidation Preference Per Share | $ / shares	$ 1,000
Preferred Stock, Dividend Rate, Percentage	9.00%
Asset
Cash and cash equivalents	$ 174,082,000
Investment securities	311,812,000
Loans held for sale	19,864,000
Loans	2,275,682,000
Premises and equipment	76,367,000
Intangible assets	38,233,000
Mortgage servicing rights	19,156,000
Other real estate owned	13,178,000
FDIC receivable for loss sharing agreement	21,713,000
Bank owned life insurance	51,020,000
Deferred tax asset	32,877,000
Other assets	45,379,000
Total assets	3,079,363,000
Deposits:
Noninterest-bearing	430,517,000
Interest-bearing	2,091,296,000
Total deposits	2,521,813,000
Other borrowings	301,713,000
Other liabilities	23,280,000
Total liabilities	2,846,806,000
Net identifiable assets acquired over (under) liabilities assumed	232,557,000
Goodwill	214,396,000
Net assets acquired over liabilities assumed	$ 446,953,000
Consideration:
Noncash Merger Related Costs		$ 23,900,000
Provision for Loan and Lease Losses				6,400,000
First Financial Holdings, Inc. ("First Financial") | As previously recorded by acquiree
Mergers and Acquisitions
Common shares issued | shares	7,018,274
Asset
Cash and cash equivalents	$ 174,082,000
Investment securities	313,200,000
Loans held for sale	19,858,000
Loans	2,355,527,000
Premises and equipment	82,399,000
Intangible assets	7,037,000
Mortgage servicing rights	19,156,000
Other real estate owned	13,271,000
FDIC receivable for loss sharing agreement	47,459,000
Bank owned life insurance	51,513,000
Deferred tax asset	(5,279,000)
Other assets	47,257,000
Total assets	3,125,480,000
Deposits:
Noninterest-bearing	430,517,000
Interest-bearing	2,083,495,000
Total deposits	2,514,012,000
Other borrowings	280,187,000
Other liabilities	25,584,000
Total liabilities	2,819,783,000
Net identifiable assets acquired over (under) liabilities assumed	305,697,000
Net assets acquired over liabilities assumed	$ 305,697,000
Consideration:
Purchase price per share of the Company's common stock (in dollars per share) | $ / shares	$ 54.34
Company common stock issued and cash exchanged for fractional shares	$ 381,423,000
Cash paid for stock options outstanding	530,000
Assumption of preferred stock	65,000,000
Fair value of total consideration transferred	446,953,000
First Financial Holdings, Inc. ("First Financial") | Initial Fair Value Adjustments
Asset
Investment securities	(1,388,000)
Loans held for sale	6,000
Loans	(92,720,000)
Premises and equipment	(5,435,000)
Intangible assets	33,738,000
Other real estate owned	(2,065,000)
FDIC receivable for loss sharing agreement	(18,122,000)
Deferred tax asset	42,741,000
Other assets	(6,125,000)
Total assets	(49,370,000)
Deposits:
Interest-bearing	7,801,000
Total deposits	7,801,000
Other borrowings	21,526,000
Other liabilities	(2,059,000)
Total liabilities	27,268,000
Net identifiable assets acquired over (under) liabilities assumed	(76,638,000)
Goodwill	217,894,000
Net assets acquired over liabilities assumed	141,256,000
First Financial Holdings, Inc. ("First Financial") | Subsequent Fair Value Adjustments
Asset
Loans	12,875,000
Premises and equipment	(597,000)
Intangible assets	(2,542,000)
Other real estate owned	1,972,000
FDIC receivable for loss sharing agreement	(7,624,000)
Bank owned life insurance	(493,000)
Deferred tax asset	(4,585,000)
Other assets	4,247,000
Total assets	3,253,000
Deposits:
Other liabilities	(245,000)
Total liabilities	(245,000)
Net identifiable assets acquired over (under) liabilities assumed	3,498,000
Goodwill	$ (3,498,000)
Savannah Bancorp and FFHI
Consideration:
Merger-related expense				$ 22,500,000