Acquisitions (Details Textuals) $ / shares in Units, $ in Thousands	Jul. 01, 2016 USD ($) Branches $ / shares	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Business Acquisition [Line Items]
Goodwill	$ 131,312	$ 142,025	$ 130,612	$ 123,566	$ 14,527	$ 1,509
Tidelands Bancshares Inc
Business Acquisition [Line Items]
Number of branches | Branches	7
Cash price per share | $ / shares	$ 0.52
Cash payment for acquisition	$ 2,220
Unpaid dividend	8,980
Core deposit intangible	$ 1,570
Expected useful life of asset	5 years
Tidelands Bancshares Inc | As Recorded by Tidelands
Business Acquisition [Line Items]
Assets acquired	$ 445,884
Liabilities assumed	447,129
Long-term debt	14,434
Tidelands Bancshares Inc | As Recorded by Tidelands | Trust I
Business Acquisition [Line Items]
Long-term debt	$ 8,250
Description of variable rate basis	LIBOR
Spread on variable rate	1.38%
Tidelands Bancshares Inc | As Recorded by Tidelands | Trust II
Business Acquisition [Line Items]
Long-term debt	$ 6,190
Description of variable rate basis	LIBOR
Spread on variable rate	5.075%
Tidelands Bancshares Inc | As Recorded by United
Business Acquisition [Line Items]
Assets acquired	$ 440,245
Liabilities assumed	439,749
Goodwill	10,713
Long-term debt	$ 10,766