Mergers and Acquisitions-Additional Information (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 01, 2013		Feb. 04, 2011	Jul. 23, 2010	Dec. 10, 2014 Branches	Jan. 20, 2015	Aug. 30, 2013 Branches	Aug. 31, 2011 Trust
Business Acquisition [Line Items]
Goodwill	$ 274,706,000	$ 276,100,000	$ 184,859,000
Variable interest rate of derivatives, description	the three-month LIBOR plus pre-determined spread
Merger-related expenses	694,000	6,027,000	0
Value of loans covered in loss-share agreements with the FDIC						73,657,000	361,472,000
Value of other real estate owned covered In loss share agreements with federal deposit insurance corporation							50,168,000
Percentage of eligible losses (percent)	80.00%
Percentage of eligible recoveries (percent)	80.00%
Heritage Financial Group
Business Acquisition [Line Items]
Total assets acquired								1,932,425,000
Loans acquired								1,288,635,000
Deposits assumed								1,577,526,000
Number of banking, mortgage, and investment offices (branches)								48
Heritage Financial Group | Subsequent Event [Member] | Norcross, Georgia [Member]
Business Acquisition [Line Items]
Loans acquired									39,600,000
Deposits assumed									129,000,000
First M&F
Business Acquisition [Line Items]
Total assets acquired				1,516,603,000
Number of banking and insurance locations (branches)										43
Shares issued to common shareholders (shares)				6,175,576
Percentage of voting interests acquired (percent)				100.00%
Total purchase price				156,845,000
Intangible assets				115,159,000
Goodwill				90,127,000	[1]
Intangible Assets, other than goodwill				25,032,000
Borrowings				25,346,000
Junior subordinated debentures				12,371,000
Merger-related expenses				1,321,000
First M&F | Core deposit intangible
Business Acquisition [Line Items]
Useful life (in years)				10 years
First M&F | Junior subordinated debentures
Business Acquisition [Line Items]
Borrowings				30,928,000
Variable interest rate of derivatives, description				90-day LIBOR
Junior subordinated debentures				12,371,000
First M&F | 90-day LIBOR | Junior subordinated debentures
Business Acquisition [Line Items]
Basis spread on variable rate (percent)				1.33%
RBC Bank (USA)
Business Acquisition [Line Items]
Assets under management											$ 680,000,000
Trust transferred under acquisition (trust)											200
American Trust Bank
Business Acquisition [Line Items]
Number of branches in the northwest region of Georgia (branches)						3

[1] The goodwill resulting from the merger has been assigned to the Community Banks operating segment.