Loans and Allowance for Loan Losses - Aggregated analysis of the changes in allowance for loan losses - (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in allowance for loan losses
Balance at beginning of period	$ 37,796,000	$ 41,904,000	$ 45,949,000
Loans charged-off	(6,889,000)	(8,967,000)	(9,047,000)
Recoveries of loans previously charged off	3,551,000	3,188,000	3,178,000
Net charge-offs	(3,338,000)	(5,779,000)	(5,869,000)
Provision (benefit)	6,796,000	5,078,000	4,170,000
Benefits attributable to FDIC loss share agreements	23,000	786,000	2,420,000
Total provision for loan losses charged to operations	6,819,000	5,864,000	6,590,000
Provision for loan losses recorded through the FDIC loss share receivable	(23,000)	(786,000)	(2,420,000)
Reduction due to loan removals	(899,000)	(3,407,000)	(2,346,000)
Balance at the end of the period	0
Balance at end of period	40,355,000	37,796,000	41,904,000
Non-acquired loans
Changes in allowance for loan losses
Balance at beginning of period	34,090,000	34,539,000	34,331,000
Loans charged-off	(5,902,000)	(6,180,000)	(7,516,000)
Recoveries of loans previously charged off	3,233,000	2,801,000	2,574,000
Net charge-offs	(2,669,000)	(3,379,000)	(4,942,000)
Provision (benefit)	5,539,000	2,930,000	5,150,000
Total provision for loan losses charged to operations	5,539,000	2,930,000	5,150,000
Balance at end of period	36,960,000	34,090,000	34,539,000
Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(987,000)	(2,787,000)	(1,531,000)
Recoveries of loans previously charged off	318,000	387,000	604,000
Net charge-offs	(669,000)	(2,400,000)	(927,000)
Provision (benefit)	669,000	2,400,000	927,000
Total provision for loan losses charged to operations	669,000	2,400,000	927,000
Acquired credit impaired loans
Changes in allowance for loan losses
Balance at beginning of period	3,706,000	7,365,000	11,618,000
Balance at the beginning of the period	3,706,000	7,365,000	11,618,000
Provision (benefit)	588,000	(252,000)	(1,907,000)
Benefits attributable to FDIC loss share agreements	23,000	786,000	2,420,000
Total provision for loan losses charged to operations	611,000	534,000	513,000
Provision for loan losses recorded through the FDIC loss share receivable	(23,000)	(786,000)	(2,420,000)
Reduction due to loan removals	(899,000)	(3,407,000)	(2,346,000)
Balance at the end of the period	3,395,000	3,706,000	7,365,000
Balance at end of period	$ 3,395,000	$ 3,706,000	$ 7,365,000