Mergers and Acquisitions - (Details) $ / shares in Units, $ in Thousands		Jul. 01, 2015 USD ($) Branches $ / shares shares	Sep. 01, 2013 USD ($) Branches shares	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 30, 2014 USD ($)	Aug. 31, 2011 USD ($) Trust	Feb. 04, 2011 USD ($) Branches	Jul. 23, 2010 USD ($) Branches
Business Acquisition [Line Items]
Goodwill resulting from merger				$ 274,698	$ 274,706	$ 276,146
Eligible losses covered (percent)				80.00%
Eligible recoveries covered (percent)				80.00%
First M&F Merger
Business Acquisition [Line Items]
Total Purchase Price			$ 156,845
Shares issued to common shareholders | shares			6,175,576
Voting interest acquired (percent)			100.00%
Total assets			$ 1,516,603
Number of banking and insurance locations the entity operates (branches) | Branches			43
Intangible assets, including goodwill			$ 115,159
Goodwill resulting from merger	[1]		90,127
Borrowings			25,346
First M&F Merger | Core Deposits
Business Acquisition [Line Items]
Intangible assets, other than goodwill			$ 25,032
Weighted average useful life			10 years
First M&F Merger | Junior Subordinated Debt
Business Acquisition [Line Items]
Borrowings			$ 30,928
Variable interest rate of derivatives, description			90-day LIBOR
Fair value adjustment			$ 12,371
First M&F Merger | LIBOR | Junior Subordinated Debt
Business Acquisition [Line Items]
Basis spread on variable rate (percent)			1.33%
First M&F Merger | Common Stock
Business Acquisition [Line Items]
Shares issued to common shareholders | shares			6,175,576
Royal Bank Client
Business Acquisition [Line Items]
Assets under management							$ 680,000
Trust transferred under acquisition (trust) | Trust							200
American Trust Bank
Business Acquisition [Line Items]
Number of branches in the northwest region of Georgia (branches) | Branches								3
Value of loans covered in loss-share agreements with the FDIC								$ 73,657
Eligible losses covered (percent)				80.00%
Eligible recoveries covered (percent)				80.00%
Crescent Bank & Trust Company
Business Acquisition [Line Items]
Number of branches in the northwest region of Georgia (branches) | Branches									11
Value of loans covered in loss-share agreements with the FDIC									$ 361,472
Other real estate owned									$ 50,168
Eligible losses covered (percent)				80.00%
Subsequent Event [Member] | Heritage Financial Group
Business Acquisition [Line Items]
Total Purchase Price		$ 287,471
Payment to Heritage stock option holders		$ 5,915
Voting interest acquired (percent)		100.00%
Cash paid for each share of the acquired entity's shares, factor in excess of exercise price (usd per share) | $ / shares		$ 27.00
Total assets		$ 1,870
Loans acquired		1,138
Deposits assumed		$ 1,372
Number of banking, mortgage, and investment offices (branches) | Branches		48
Subsequent Event [Member] | Heritage Financial Group | Common Stock
Business Acquisition [Line Items]
Shares issued to common shareholders | shares		8,636,677
Number of shares for each share of acquired entity's shares		0.9266

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