Loans - Schedule of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Allowance for loan losses
Allowance for loan losses, beginning of period	$ 35,625	$ 34,344	$ 33,293	$ 40,686
Provision	1,060	(1,168)	2,340	(2,450)
Charge-offs	(11)	(231)	(319)	(6,654)
Net recoveries of impaired loans	176	584	1,536	1,947
Allowance for loan losses, end of period	36,850	33,529	36,850	33,529
Commercial
Allowance for loan losses
Allowance for loan losses, beginning of period	15,749	17,349	15,398	24,215
Provision	437	(1,247)	829	(2,306)
Charge-offs		(227)	(222)	(6,630)
Net recoveries of impaired loans	165	460	346	1,056
Allowance for loan losses, end of period	16,351	16,335	16,351	16,335
Real estate - mortgage
Allowance for loan losses
Allowance for loan losses, beginning of period	12,804	10,281	11,475	10,372
Provision	(167)	247	998	138
Net recoveries of impaired loans	3	9	167	27
Allowance for loan losses, end of period	12,640	10,537	12,640	10,537
Construction and land
Allowance for loan losses
Allowance for loan losses, beginning of period	2,484	2,335	1,997	2,111
Provision	958	(250)	437	(765)
Net recoveries of impaired loans	4	101	1,012	840
Allowance for loan losses, end of period	3,446	2,186	3,446	2,186
Consumer
Allowance for loan losses
Allowance for loan losses, beginning of period	2,561	2,660	2,803	2,592
Provision	(9)	109	(172)	187
Charge-offs	(11)		(97)	(20)
Net recoveries of impaired loans	4	14	11	24
Allowance for loan losses, end of period	2,545	2,783	2,545	2,783
Other
Allowance for loan losses
Allowance for loan losses, beginning of period	1,021	786	945	643
Provision	(40)	119	36	262
Charge-offs		(4)		(4)
Allowance for loan losses, end of period	981	901	981	901
Unallocated
Allowance for loan losses
Allowance for loan losses, beginning of period	1,006	933	675	753
Provision	(119)	(146)	212	34
Allowance for loan losses, end of period	$ 887	$ 787	$ 887	$ 787