Mergers and Acquisitions - (Details 2) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		6 Months Ended
		Jul. 01, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Value of stock paid					$ 55,290	$ 0
Deal charges			$ 2,807	$ 1,467	3,755	1,946
Goodwill resulting from merger			$ 470,534	$ 274,698	$ 470,534	$ 274,698	$ 445,871
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		5,915
Compensation expense incurred from the termination of Heritage's ESOP		0
Deal charges		7,973
Total Purchase Price		295,444
Stockholders’ equity at acquisition date		160,652
Total Net Assets Acquired		120,232
Goodwill resulting from merger	[1]	175,212
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		(7,873)
Heritage Financial Group | Deferred income taxes
Business Acquisition [Line Items]
Fair value adjustment of liabilities		(8,077)
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		(3,158)
Loans, net of Heritage's allowance for loan losses | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		(16,837)
Fixed assets | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		(6,419)
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 | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		(15,507)
Other assets | Heritage Financial Group
Business Acquisition [Line Items]
Fair value adjustment of assets		$ 3,045

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