Mergers and Acquisitions - Purchase Price Adjustment (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended		9 Months Ended
		Jul. 01, 2015	Sep. 01, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Business Acquisition [Line Items]
Deal charges				$ 7,746	$ 0	$ 9,691	$ 195
Goodwill resulting from merger				$ 452,037	$ 274,658	$ 452,037	$ 274,658	$ 274,706
Heritage Financial Group
Business Acquisition [Line Items]
Purchase price per share (usd per share)		$ 32.60
Value of stock paid		$ 281,530
Cash paid for fractional shares		26
Cash settlement for stock options, net of tax benefit		3,697
Compensation expense incurred from the termination of Heritage's ESOP		4,930
Total Purchase Price		297,260
Stockholders’ equity at acquisition date		160,652
Total Net Assets Acquired		119,927
Goodwill resulting from merger	[1]	177,333
Heritage Financial Group | Deposits
Business Acquisition [Line Items]
Fair value adjustment of liabilities		(3,776)
Heritage Financial Group | Other liabilities
Business Acquisition [Line Items]
Fair value adjustment of liabilities		(2,329)
Heritage Financial Group | Deferred income taxes
Business Acquisition [Line Items]
Fair value adjustment of liabilities		(13,311)
First M&F Merger
Business Acquisition [Line Items]
Deal charges		7,077
Total Purchase Price			$ 157
Goodwill resulting from merger			$ 90
Securities | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		(1,401)
Mortgage loans held for sale | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		(2,481)
Loans, net of First M&F's allowance for loan losses | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		(15,803)
Fixed assets | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		(7,253)
Intangible assets, net of Heritage's existing core deposit intangible | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		18,193
Other real estate owned | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		1,390
FDIC Loss Share Indemnification Asset [Member] | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		(15,247)
Other assets | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		$ 1,293

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