Loans and Allowance for Loan Losses - Disaggregated analysis of activity in the allowance for acquired credit impaired loans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Allowance for loan losses:
Provision for loan losses before benefit attributable to FDIC loss share agreements		$ 2,728	$ 6,020	$ 5,263
Total provision for loan losses charged to operations	$ 2,313	2,728	6,020	5,286
Provision for loan losses recorded through the FDIC loss share receivable				(23)
Reduction due to loan removals	(243)	(172)	(346)	(349)
Non-acquired loans
Allowance for loan losses:
Provision for loan losses before benefit attributable to FDIC loss share agreements		2,500	4,573	4,480
Total provision for loan losses charged to operations	2,456	2,500	4,573	4,480
Loans individually evaluated for impairment	2,300	1,507	2,300	1,507
Loans collectively evaluated for impairment	37,849	35,432	37,849	35,432
Loans:
Loans individually evaluated for impairment	49,120	24,323	49,120	24,323
Loans collectively evaluated for impairment	5,943,273	4,792,552	5,943,273	4,792,552
Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	4,556	3,877	3,395	3,706
Provision for loan losses before benefit attributable to FDIC loss share agreements	(572)	47	692	395
Benefits attributable to FDIC loss share agreements				23
Total provision for loan losses charged to operations	(572)	47	692	418
Provision for loan losses recorded through the FDIC loss share receivable				(23)
Reduction due to loan removals	(243)	(172)	(346)	(349)
Balance at the end of the period	3,741	3,752	3,741	3,752
Loans collectively evaluated for impairment	3,741	3,752	3,741	3,752
Loans:
Loans collectively evaluated for impairment	606,222	662,587	606,222	662,587
Carrying value	606,222	662,587	606,222	662,587	$ 605,941
Other commercial non-owner occupied real estate | Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations			1,136	1,057
Other commercial non-owner occupied real estate | Acquired credit impaired loans
Loans:
Carrying value					210,204
Residential real estate | Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	3,108	2,863	2,419	2,986
Provision for loan losses before benefit attributable to FDIC loss share agreements	(192)	(165)	559	(180)
Benefits attributable to FDIC loss share agreements				23
Total provision for loan losses charged to operations	(192)	(165)	559	(157)
Provision for loan losses recorded through the FDIC loss share receivable				(23)
Reduction due to loan removals	(175)	(106)	(237)	(214)
Balance at the end of the period	2,741	2,592	2,741	2,592
Loans collectively evaluated for impairment	2,741	2,592	2,741	2,592
Loans:
Loans collectively evaluated for impairment	256,602	285,518	256,602	285,518
Carrying value	256,602	285,518	256,602	285,518	258,100
Commercial non-owner occupied real estate | Construction and land development | Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	1,098	(100)
Loans individually evaluated for impairment	1,310	751	1,310	751
Loans collectively evaluated for impairment	4,436	3,914	4,436	3,914
Loans:
Loans individually evaluated for impairment	30,037	4,093	30,037	4,093
Loans collectively evaluated for impairment	682,205	529,126	682,205	529,126
Commercial non-owner occupied real estate | Construction and land development | Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	130	154
Reduction due to loan removals	(38)	(3)
Balance at the end of the period	92	151	92	151
Loans collectively evaluated for impairment	92	151	92	151
Loans:
Loans collectively evaluated for impairment	52,977	48,274	52,977	48,274
Carrying value	52,977	48,274	52,977	48,274	44,373
Commercial non-owner occupied real estate | Other commercial non-owner occupied real estate | Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	693	718
Loans individually evaluated for impairment	146	202	146	202
Loans collectively evaluated for impairment	6,018	4,454	6,018	4,454
Loans:
Loans individually evaluated for impairment	754	1,219	754	1,219
Loans collectively evaluated for impairment	952,157	585,609	952,157	585,609
Commercial non-owner occupied real estate | Other commercial non-owner occupied real estate | Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	335	46
Provision for loan losses before benefit attributable to FDIC loss share agreements	(292)
Total provision for loan losses charged to operations	(292)
Reduction due to loan removals	(3)	(11)
Balance at the end of the period	40	35	40	35
Loans collectively evaluated for impairment	40	35	40	35
Loans:
Loans collectively evaluated for impairment	206,271	225,460	206,271	225,460
Carrying value	206,271	225,460	206,271	225,460	210,204
Consumer real estate | Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	589	606
Provision for loan losses before benefit attributable to FDIC loss share agreements	(37)	217
Total provision for loan losses charged to operations	(37)	217
Reduction due to loan removals	(4)	(45)
Balance at the end of the period	548	778	548	778
Loans collectively evaluated for impairment	548	778	548	778
Loans:
Loans collectively evaluated for impairment	56,362	64,114	56,362	64,114
Carrying value	56,362	64,114	56,362	64,114	59,300
Consumer real estate | Home equity loans | Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	(40)	288
Loans individually evaluated for impairment	119	38	119	38
Loans collectively evaluated for impairment	3,128	3,110	3,128	3,110
Loans:
Loans individually evaluated for impairment	2,626	2,177	2,626	2,177
Loans collectively evaluated for impairment	408,906	343,780	408,906	343,780
Commercial and industrial | Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	43	283	257	519
Loans individually evaluated for impairment	362	14	362	14
Loans collectively evaluated for impairment	4,781	4,255	4,781	4,255
Loans:
Loans individually evaluated for impairment	1,198	767	1,198	767
Loans collectively evaluated for impairment	761,385	611,134	761,385	611,134
Commercial and industrial | Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period	394	208	238	174
Provision for loan losses before benefit attributable to FDIC loss share agreements	(51)	(5)	136	40
Total provision for loan losses charged to operations	(51)	(5)	136	40
Reduction due to loan removals	(23)	(7)	(54)	(18)
Balance at the end of the period	320	196	320	196
Loans collectively evaluated for impairment	320	196	320	196
Loans:
Loans collectively evaluated for impairment	25,486	27,961	25,486	27,961
Carrying value	25,486	27,961	25,486	27,961	25,347
Other income producing property | Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	36	(18)	(204)	(183)
Loans individually evaluated for impairment	238	376	238	376
Loans collectively evaluated for impairment	1,141	1,436	1,141	1,436
Loans:
Loans individually evaluated for impairment	3,641	5,000	3,641	5,000
Loans collectively evaluated for impairment	185,685	176,703	185,685	176,703
Consumer | Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations	719	872
Loans individually evaluated for impairment	6	4	6	4
Loans collectively evaluated for impairment	2,526	2,010	2,526	2,010
Loans:
Loans individually evaluated for impairment	235	128	235	128
Loans collectively evaluated for impairment	357,526	272,829	357,526	272,829
Consumer | Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period			558	313
Provision for loan losses before benefit attributable to FDIC loss share agreements				534
Total provision for loan losses charged to operations				534
Reduction due to loan removals			(10)	(69)
Balance at the end of the period	548	778	548	778
Loans:
Carrying value	56,362	64,114	56,362	64,114	59,300
Consumer | Home equity loans | Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations			165	811
Commercial loans 1000000 or more | Acquired credit impaired loans
Loans:
Loans collectively evaluated for impairment	8,524	11,260	8,524	11,260
Carrying value	8,524	11,260	8,524	11,260	$ 8,617
Commercial | Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period			41	56
Provision for loan losses before benefit attributable to FDIC loss share agreements				1
Total provision for loan losses charged to operations				1
Reduction due to loan removals			(1)	(22)
Balance at the end of the period	40	35	40	35
Commercial | Construction and land development | Non-acquired loans
Allowance for loan losses:
Total provision for loan losses charged to operations			1,907	101
Commercial | Construction and land development | Acquired credit impaired loans
Allowance for loan losses:
Balance at the beginning of the period			139	177
Provision for loan losses before benefit attributable to FDIC loss share agreements			(3)
Total provision for loan losses charged to operations			(3)
Reduction due to loan removals			(44)	(26)
Balance at the end of the period	$ 92	$ 151	$ 92	$ 151