Loans and Allowance for Loan Losses - Disaggregated analysis of activity in for allowances for non acquired loans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Allowance for loan losses:
Charge-offs	$ (2,862)	$ (2,423)	$ (4,481)	$ (3,926)
Recoveries	991	1,138	1,949	2,105
Provision (benefit)	3,704	4,478	5,192	6,932
Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	52,008	45,203	51,194	43,448
Charge-offs	(1,327)	(1,240)	(2,572)	(2,409)
Recoveries	875	1,051	1,627	1,853
Provision (benefit)	2,034	2,860	3,341	4,982
Balance at end of period	53,590	47,874	53,590	47,874
Loans individually evaluated for impairment	1,384	1,829	1,384	1,829
Loans collectively evaluated for impairment	52,206	46,045	52,206	46,045
Loans:
Loans individually evaluated for impairment	54,509	62,593	54,509	62,593
Loans collectively evaluated for impairment	8,566,818	7,134,946	8,566,818	7,134,946
Total loans	8,621,327	7,197,539	8,621,327	7,197,539	$ 7,933,286
Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs	(1,535)	(1,183)	(1,909)	(1,517)
Recoveries	116	87	322	252
Provision (benefit)	1,419	1,096	1,587	1,265
Loans:
Loans collectively evaluated for impairment	2,180,281	3,076,424	2,180,281	3,076,424
Total loans	2,180,281	3,076,424	2,180,281	3,076,424	2,594,826
Commercial non-owner occupied real estate | Non-acquired loans
Loans:
Total loans	2,603,364	2,042,125	2,603,364	2,042,125	2,256,996
Commercial non-owner occupied real estate | Non-acquired loans | Construction and land development
Allowance for loan losses:
Balance at beginning of period	5,371	5,847	5,682	5,921
Charge-offs	(9)		(9)	(35)
Recoveries	326	547	625	989
Provision (benefit)	30	(207)	(580)	(688)
Balance at end of period	5,718	6,187	5,718	6,187
Loans individually evaluated for impairment	715	846	715	846
Loans collectively evaluated for impairment	5,003	5,341	5,003	5,341
Loans:
Loans individually evaluated for impairment	36,130	42,392	36,130	42,392
Loans collectively evaluated for impairment	843,594	864,498	843,594	864,498
Total loans	879,724	906,890	879,724	906,890	841,445
Commercial non-owner occupied real estate | Non-acquired loans | Other commercial non-owner occupied real estate
Allowance for loan losses:
Balance at beginning of period	9,740	6,798	8,754	6,525
Charge-offs	(3)		(3)
Recoveries	23	2	45	4
Provision (benefit)	551	409	1,515	680
Balance at end of period	10,311	7,209	10,311	7,209
Loans individually evaluated for impairment	1	93	1	93
Loans collectively evaluated for impairment	10,310	7,116	10,310	7,116
Loans:
Loans individually evaluated for impairment	101	1,348	101	1,348
Loans collectively evaluated for impairment	1,723,539	1,133,887	1,723,539	1,133,887
Total loans	1,723,640	1,135,235	1,723,640	1,135,235	1,415,551
Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Construction and land development
Allowance for loan losses:
Charge-offs		(106)	(6)	(107)
Recoveries	1	6	2	7
Provision (benefit)	(1)	100	4	100
Loans:
Loans collectively evaluated for impairment	60,391	281,282	60,391	281,282
Total loans	60,391	281,282	60,391	281,282	165,070
Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate
Loans:
Loans collectively evaluated for impairment	595,367	752,465	595,367	752,465
Total loans	595,367	752,465	595,367	752,465	679,253
Commercial owner occupied real estate loan | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	9,629	8,346	9,369	8,128
Charge-offs		(81)	(12)	(81)
Recoveries	41	25	66	33
Provision (benefit)	(144)	317	103	527
Balance at end of period	9,526	8,607	9,526	8,607
Loans individually evaluated for impairment	33	44	33	44
Loans collectively evaluated for impairment	9,493	8,563	9,493	8,563
Loans:
Loans individually evaluated for impairment	5,440	4,750	5,440	4,750
Loans collectively evaluated for impairment	1,584,547	1,367,703	1,584,547	1,367,703
Total loans	1,589,987	1,372,453	1,589,987	1,372,453	1,517,551
Commercial owner occupied real estate loan | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs	(786)	(28)	(786)	(28)
Provision (benefit)	786	28	786	28
Loans:
Loans collectively evaluated for impairment	376,187	486,254	376,187	486,254
Total loans	376,187	486,254	376,187	486,254	421,841
Consumer loans | Non-acquired loans
Loans:
Total loans	2,594,191	2,190,870	2,594,191	2,190,870	2,431,413
Consumer loans | Non-acquired loans | Home equity loans
Allowance for loan losses:
Balance at beginning of period	3,273	3,237	3,434	3,250
Charge-offs		(5)	(15)	(71)
Recoveries	98	27	134	128
Provision (benefit)	(194)	109	(376)	61
Balance at end of period	3,177	3,368	3,177	3,368
Loans individually evaluated for impairment	125	180	125	180
Loans collectively evaluated for impairment	3,052	3,188	3,052	3,188
Loans:
Loans individually evaluated for impairment	2,436	3,144	2,436	3,144
Loans collectively evaluated for impairment	511,806	453,802	511,806	453,802
Total loans	514,242	456,946	514,242	456,946	495,148
Consumer loans | Non-acquired loans | Consumer Owner Occupied Loans
Allowance for loan losses:
Balance at beginning of period	12,058	10,193	11,913	9,668
Charge-offs	(48)		(85)	(4)
Recoveries	30	41	32	64
Provision (benefit)	392	711	572	1,217
Balance at end of period	12,432	10,945	12,432	10,945
Loans individually evaluated for impairment	35	30	35	30
Loans collectively evaluated for impairment	12,397	10,915	12,397	10,915
Loans:
Loans individually evaluated for impairment	5,566	5,628	5,566	5,628
Loans collectively evaluated for impairment	2,074,383	1,728,296	2,074,383	1,728,296
Total loans	2,079,949	1,733,924	2,079,949	1,733,924	1,936,265
Consumer loans | Acquired non-credit impaired loans | Home equity loans
Allowance for loan losses:
Charge-offs	(168)	(158)
Recoveries	24	28
Provision (benefit)	144	130
Loans:
Loans collectively evaluated for impairment	208,777	278,906	208,777	278,906
Total loans	208,777	278,906	208,777	278,906	242,425
Consumer loans | Acquired non-credit impaired loans | Consumer Owner Occupied Loans
Allowance for loan losses:
Charge-offs	(6)		(6)	(70)
Recoveries	3	5	5	62
Provision (benefit)	3	(5)	1	8
Loans:
Loans collectively evaluated for impairment	577,284	676,596	577,284	676,596
Total loans	577,284	676,596	577,284	676,596	628,813
Commercial and industrial | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	7,249	6,333	7,454	5,488
Charge-offs	(90)	(59)	(109)	(144)
Recoveries	138	199	209	214
Provision (benefit)	198	238	(59)	1,153
Balance at end of period	7,495	6,711	7,495	6,711
Loans individually evaluated for impairment	394	485	394	485
Loans collectively evaluated for impairment	7,101	6,226	7,101	6,226
Loans:
Loans individually evaluated for impairment	2,674	1,834	2,674	1,834
Loans collectively evaluated for impairment	1,111,839	939,233	1,111,839	939,233
Total loans	1,114,513	941,067	1,114,513	941,067	1,054,952
Commercial and industrial | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs	(506)	(764)	(640)	(807)
Recoveries	6	2	171	55
Provision (benefit)	500	762	469	752
Loans:
Loans collectively evaluated for impairment	151,579	304,864	151,579	304,864
Total loans	151,579	304,864	151,579	304,864	212,537
Other income producing property | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	1,387	1,393	1,446	1,375
Charge-offs	(31)		(31)
Recoveries	13	3	58	11
Provision (benefit)	(10)	17	(114)	27
Balance at end of period	1,359	1,413	1,359	1,413
Loans individually evaluated for impairment	78	144	78	144
Loans collectively evaluated for impairment	1,281	1,269	1,281	1,269
Loans:
Loans individually evaluated for impairment	2,064	3,240	2,064	3,240
Loans collectively evaluated for impairment	212,139	202,267	212,139	202,267
Total loans	214,203	205,507	214,203	205,507	214,353
Other income producing property | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs			(26)
Recoveries	71		71
Provision (benefit)	(71)		(45)
Loans:
Loans collectively evaluated for impairment	111,006	169,392	111,006	169,392
Total loans	111,006	169,392	111,006	169,392	133,110
Consumer | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	3,195	2,899	3,101	2,788
Charge-offs	(1,146)	(1,095)	(2,308)	(2,074)
Recoveries	206	207	458	410
Provision (benefit)	1,317	1,060	2,321	1,947
Balance at end of period	3,572	3,071	3,572	3,071
Loans individually evaluated for impairment	3	7	3	7
Loans collectively evaluated for impairment	3,569	3,064	3,569	3,064
Loans:
Loans individually evaluated for impairment	98	257	98	257
Loans collectively evaluated for impairment	503,370	416,393	503,370	416,393
Total loans	503,468	416,650	503,468	416,650	448,664
Consumer | Non-acquired loans | Consumer
Loans:
Total loans	503,468	416,650	503,468	416,650	448,664
Consumer | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs	(69)	(127)	(205)	(265)
Recoveries	11	46	27	49
Provision (benefit)	58	81	178	216
Loans:
Loans collectively evaluated for impairment	99,690	126,665	99,690	126,665
Total loans	99,690	126,665	99,690	126,665	111,777
Commercial loans | Non-acquired loans
Loans:
Total loans	5,522,067	4,561,152	5,522,067	4,561,152	5,043,852
Commercial loans | Acquired non-credit impaired loans | Home equity loans
Allowance for loan losses:
Charge-offs			(240)	(240)
Recoveries			46	79
Provision (benefit)			194	161
Other loans | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	106	157	41	305
Provision (benefit)	(106)	206	(41)	58
Balance at end of period		363		363
Loans collectively evaluated for impairment		363		363
Loans:
Loans collectively evaluated for impairment	1,601	28,867	1,601	28,867
Total loans	$ 1,601	$ 28,867	$ 1,601	$ 28,867	$ 9,357