Loans and Allowance for Loan Losses - Summary of acquired non credit impaired loans - (Details 2) - USD ($)	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loans and Allowance for Loan Losses
Less allowance for loan losses	$ 0
Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	1,049,538,000	$ 1,327,999,000
Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	737,576,000	926,767,000	$ 1,232,256,000
Less allowance for loan losses	(3,706,000)	(7,365,000)	(11,618,000)	$ (17,218,000)
Acquired loans, net	733,870,000	919,402,000	1,220,638,000	969,395,000
Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	1,049,538,000	1,327,999,000
Acquired credit impaired loans accounted under FASB 310 30
Loans and Allowance for Loan Losses
Total acquired loans	737,576,000	926,767,000
Less allowance for loan losses	(3,706,000)	(7,365,000)
Acquired loans, net	733,870,000	919,402,000
Commercial Loans Greater Than or Equal to $1 Million-CBT | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	12,628,000	15,813,000	24,109,000
Less allowance for loan losses		(135,000)	(303,000)	(5,337,000)
Commercial Loans Greater Than or Equal to $1 Million-CBT | Acquired credit impaired loans accounted under FASB 310 30
Loans and Allowance for Loan Losses
Total acquired loans	12,628,000	15,813,000
Residential real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	313,319,000	390,244,000	481,247,000
Less allowance for loan losses	(2,986,000)	(4,387,000)	(5,132,000)	(4,207,000)
Residential real estate | Acquired credit impaired loans accounted under FASB 310 30
Loans and Allowance for Loan Losses
Total acquired loans	313,319,000	390,244,000
Commercial non-owner occupied real estate | Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	53,952,000	73,575,000
Consumer real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	879,722,000	1,086,090,000
Consumer real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	70,734,000	85,449,000	103,998,000
Less allowance for loan losses	(313,000)	(275,000)	(538,000)	(96,000)
Consumer real estate | Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	709,075,000	881,324,000
Commercial owner occupied real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	39,220,000	62,065,000
Commercial owner occupied real estate | Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	39,220,000	62,065,000
Commercial and industrial | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	25,475,000	41,130,000
Commercial and industrial | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	31,193,000	44,804,000	68,862,000
Less allowance for loan losses	(174,000)	(718,000)	(1,481,000)	(4,139,000)
Commercial and industrial | Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	25,475,000	41,130,000
Commercial and industrial | Acquired credit impaired loans accounted under FASB 310 30
Loans and Allowance for Loan Losses
Total acquired loans	31,193,000	44,804,000
Single pay | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans		86,000	129,000
Less allowance for loan losses		(70,000)	(104,000)	(294,000)
Single pay | Acquired credit impaired loans accounted under FASB 310 30
Loans and Allowance for Loan Losses
Total acquired loans		86,000
Other income producing property | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	51,169,000	65,139,000
Other income producing property | Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	51,169,000	65,139,000
Consumer | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	170,647,000	204,766,000
Consumer | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	70,734,000	85,449,000
Consumer | Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	170,647,000	204,766,000
Consumer | Acquired credit impaired loans accounted under FASB 310 30
Loans and Allowance for Loan Losses
Total acquired loans	70,734,000	85,449,000
Construction and land development | Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	13,849,000	24,099,000
Construction and land development | Commercial non-owner occupied real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	54,272,000	65,262,000	114,126,000
Less allowance for loan losses	(177,000)	(336,000)	(2,244,000)	(1,628,000)
Construction and land development | Commercial non-owner occupied real estate | Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	13,849,000	24,099,000
Construction and land development | Commercial non-owner occupied real estate | Acquired credit impaired loans accounted under FASB 310 30
Loans and Allowance for Loan Losses
Total acquired loans	54,272,000	65,262,000
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	40,103,000	49,476,000
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	255,430,000	325,109,000	439,785,000
Less allowance for loan losses	(56,000)	(1,444,000)	$ (1,816,000)	$ (1,517,000)
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	40,103,000	49,476,000
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired credit impaired loans accounted under FASB 310 30
Loans and Allowance for Loan Losses
Total acquired loans	255,430,000	325,109,000
Consumer owner occupied | Consumer real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	518,107,000	646,375,000
Consumer owner occupied | Consumer real estate | Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	518,107,000	646,375,000
Home equity loans | Consumer real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	190,968,000	234,949,000
Home equity loans | Consumer real estate | Acquired non-credit impaired loans accounted under FASB 310 20
Loans and Allowance for Loan Losses
Total acquired loans	$ 190,968,000	$ 234,949,000