Loans and Allowance for Loan Losses - Disaggregated analysis of activity in for allowances for non acquired loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Allowance for loan losses:
Charge-offs	$ (2,779)	$ (1,988)	$ (7,260)	$ (5,914)
Recoveries	884	582	2,833	2,687
Provision (benefit)	4,028	3,117	9,220	10,049
Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	53,590	47,874	51,194	43,448
Charge-offs	(1,969)	(1,891)	(4,541)	(4,300)
Recoveries	834	555	2,461	2,408
Provision (benefit)	2,482	3,331	5,823	8,313
Balance at end of period	54,937	49,869	54,937	49,869
Loans individually evaluated for impairment	1,221	1,657	1,221	1,657
Loans collectively evaluated for impairment	53,716	48,212	53,716	48,212
Loans:
Loans individually evaluated for impairment	54,867	54,640	54,867	54,640
Loans collectively evaluated for impairment	8,873,645	7,551,838	8,873,645	7,551,838
Total loans	8,928,512	7,606,478	8,928,512	7,606,478	$ 7,933,286
Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs	(810)	(97)	(2,719)	(1,614)
Recoveries	50	27	372	279
Provision (benefit)	760	70	2,347	1,335
Loans:
Loans collectively evaluated for impairment	1,965,603	2,786,102	1,965,603	2,786,102
Total loans	1,965,603	2,786,102	1,965,603	2,786,102	2,594,826
Commercial non-owner occupied real estate | Non-acquired loans
Loans:
Total loans	2,732,645	2,182,164	2,732,645	2,182,164	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	5,718	6,187	5,682	5,921
Charge-offs	(69)		(78)	(35)
Recoveries	208	178	833	1,167
Provision (benefit)	159	(352)	(421)	(1,040)
Balance at end of period	6,016	6,013	6,016	6,013
Loans individually evaluated for impairment	587	723	587	723
Loans collectively evaluated for impairment	5,429	5,290	5,429	5,290
Loans:
Loans individually evaluated for impairment	32,673	35,776	32,673	35,776
Loans collectively evaluated for impairment	922,645	867,060	922,645	867,060
Total loans	955,318	902,836	955,318	902,836	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	10,311	7,209	8,754	6,525
Charge-offs			(3)
Recoveries	2	2	47	6
Provision (benefit)	238	774	1,753	1,454
Balance at end of period	10,551	7,985	10,551	7,985
Loans individually evaluated for impairment		81		81
Loans collectively evaluated for impairment	10,551	7,904	10,551	7,904
Loans:
Loans individually evaluated for impairment	87	1,315	87	1,315
Loans collectively evaluated for impairment	1,777,240	1,278,013	1,777,240	1,278,013
Total loans	1,777,327	1,279,328	1,777,327	1,279,328	1,415,551
Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Construction and land development
Allowance for loan losses:
Charge-offs	(39)		(45)	(106)
Recoveries	1	1	3	8
Provision (benefit)	38	(1)	42	98
Loans:
Loans collectively evaluated for impairment	53,302	222,562	53,302	222,562
Total loans	53,302	222,562	53,302	222,562	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	503,443	684,793	503,443	684,793
Total loans	503,443	684,793	503,443	684,793	679,253
Commercial owner occupied real estate loan | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	9,526	8,607	9,369	8,128
Charge-offs	(31)	(578)	(43)	(659)
Recoveries	18	105	84	76
Provision (benefit)	456	943	559	1,532
Balance at end of period	9,969	9,077	9,969	9,077
Loans individually evaluated for impairment	33	40	33	40
Loans collectively evaluated for impairment	9,936	9,037	9,936	9,037
Loans:
Loans individually evaluated for impairment	7,135	4,551	7,135	4,551
Loans collectively evaluated for impairment	1,670,560	1,444,518	1,670,560	1,444,518
Total loans	1,677,695	1,449,069	1,677,695	1,449,069	1,517,551
Commercial owner occupied real estate loan | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs			(786)	(28)
Provision (benefit)			786	28
Loans:
Loans collectively evaluated for impairment	345,040	455,803	345,040	455,803
Total loans	345,040	455,803	345,040	455,803	421,841
Consumer loans | Non-acquired loans
Loans:
Total loans	2,639,871	2,317,584	2,639,871	2,317,584	2,431,413
Consumer loans | Non-acquired loans | Home equity loans
Allowance for loan losses:
Balance at beginning of period	3,177	3,368	3,434	3,250
Charge-offs	(100)	(40)	(115)	(111)
Recoveries	86	11	220	139
Provision (benefit)	28	102	(348)	163
Balance at end of period	3,191	3,441	3,191	3,441
Loans individually evaluated for impairment	121	171	121	171
Loans collectively evaluated for impairment	3,070	3,270	3,070	3,270
Loans:
Loans individually evaluated for impairment	2,345	3,026	2,345	3,026
Loans collectively evaluated for impairment	519,399	470,355	519,399	470,355
Total loans	521,744	473,381	521,744	473,381	495,148
Consumer loans | Non-acquired loans | Consumer Owner Occupied Loans
Allowance for loan losses:
Balance at beginning of period	12,432	10,945	11,913	9,668
Charge-offs	(10)	(76)	(95)	(80)
Recoveries	149	43	181	169
Provision (benefit)	(24)	468	548	1,623
Balance at end of period	12,547	11,380	12,547	11,380
Loans individually evaluated for impairment	33	28	33	28
Loans collectively evaluated for impairment	12,514	11,352	12,514	11,352
Loans:
Loans individually evaluated for impairment	5,127	5,420	5,127	5,420
Loans collectively evaluated for impairment	2,113,000	1,838,783	2,113,000	1,838,783
Total loans	2,118,127	1,844,203	2,118,127	1,844,203	1,936,265
Consumer loans | Acquired non-credit impaired loans | Home equity loans
Allowance for loan losses:
Charge-offs	(23)	(4)
Recoveries	9	6
Provision (benefit)	14	(2)
Loans:
Loans collectively evaluated for impairment	198,112	259,558	198,112	259,558
Total loans	198,112	259,558	198,112	259,558	242,425
Consumer loans | Acquired non-credit impaired loans | Consumer Owner Occupied Loans
Allowance for loan losses:
Charge-offs			(6)	(70)
Recoveries	21	1	26	63
Provision (benefit)	(21)	(1)	(20)	7
Loans:
Loans collectively evaluated for impairment	543,432	647,064	543,432	647,064
Total loans	543,432	647,064	543,432	647,064	628,813
Commercial and industrial | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	7,495	6,711	7,454	5,488
Charge-offs	(32)	(34)	(141)	(178)
Recoveries	77	27	286	241
Provision (benefit)	21	219	(38)	1,372
Balance at end of period	7,561	6,923	7,561	6,923
Loans individually evaluated for impairment	387	475	387	475
Loans collectively evaluated for impairment	7,174	6,448	7,174	6,448
Loans:
Loans individually evaluated for impairment	5,313	1,409	5,313	1,409
Loans collectively evaluated for impairment	1,125,534	990,433	1,125,534	990,433
Total loans	1,130,847	991,842	1,130,847	991,842	1,054,952
Commercial and industrial | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs	(648)	(30)	(1,288)	(838)
Recoveries	10	5	181	60
Provision (benefit)	638	25	1,107	778
Loans:
Loans collectively evaluated for impairment	126,092	247,922	126,092	247,922
Total loans	126,092	247,922	126,092	247,922	212,537
Other income producing property | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	1,359	1,413	1,446	1,375
Charge-offs			(31)
Recoveries	29	3	87	14
Provision (benefit)	(29)	(6)	(143)	21
Balance at end of period	1,359	1,410	1,359	1,410
Loans individually evaluated for impairment	58	133	58	133
Loans collectively evaluated for impairment	1,301	1,277	1,301	1,277
Loans:
Loans individually evaluated for impairment	2,096	2,930	2,096	2,930
Loans collectively evaluated for impairment	218,861	207,053	218,861	207,053
Total loans	220,957	209,983	220,957	209,983	214,353
Other income producing property | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs			(26)
Recoveries			71
Provision (benefit)			(45)
Loans:
Loans collectively evaluated for impairment	103,093	150,371	103,093	150,371
Total loans	103,093	150,371	103,093	150,371	133,110
Consumer | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	3,572	3,071	3,101	2,788
Charge-offs	(1,727)	(1,163)	(4,035)	(3,237)
Recoveries	265	186	723	596
Provision (benefit)	1,633	1,089	3,954	3,036
Balance at end of period	3,743	3,183	3,743	3,183
Loans individually evaluated for impairment	2	6	2	6
Loans collectively evaluated for impairment	3,741	3,177	3,741	3,177
Loans:
Loans individually evaluated for impairment	91	213	91	213
Loans collectively evaluated for impairment	524,949	438,576	524,949	438,576
Total loans	525,040	438,789	525,040	438,789	448,664
Consumer | Non-acquired loans | Consumer
Loans:
Total loans	525,040	438,789	525,040	438,789	448,664
Consumer | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs	(100)	(63)	(305)	(328)
Recoveries	9	14	36	63
Provision (benefit)	91	49	269	265
Loans:
Loans collectively evaluated for impairment	93,089	118,029	93,089	118,029
Total loans	93,089	118,029	93,089	118,029	111,777
Commercial loans | Non-acquired loans
Loans:
Total loans	5,762,144	4,833,058	5,762,144	4,833,058	5,043,852
Commercial loans | Acquired non-credit impaired loans | Home equity loans
Allowance for loan losses:
Charge-offs			(263)	(244)
Recoveries			55	85
Provision (benefit)			208	159
Other loans | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period		363	41	305
Provision (benefit)		94	(41)	152
Balance at end of period		457		457
Loans collectively evaluated for impairment		457		457
Loans:
Loans collectively evaluated for impairment	1,457	17,047	1,457	17,047
Total loans	$ 1,457	$ 17,047	$ 1,457	$ 17,047	$ 9,357