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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Allowance for loan losses:
Charge-offs	$ (2,423)	$ (1,793)	$ (3,926)	$ (3,479)
Recoveries	1,138	608	2,105	1,340
Provision (benefit)	4,478	2,313	6,932	6,020
Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	45,203	38,449	43,448	36,960
Charge-offs	(1,240)	(1,292)	(2,409)	(2,589)
Recoveries	1,051	536	1,853	1,205
Provision (benefit)	2,860	2,456	4,982	4,573
Balance at end of period	47,874	40,149	47,874	40,149
Loans individually evaluated for impairment	1,829	2,300	1,829	2,300
Loans collectively evaluated for impairment	46,045	37,849	46,045	37,849
Loans:
Loans individually evaluated for impairment	62,593	49,120	62,593	49,120
Loans collectively evaluated for impairment	7,134,946	5,943,273	7,134,946	5,943,273
Total loans	7,197,539	5,992,393	7,197,539	5,992,393	$ 6,492,155
Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs	(1,183)	(501)	(1,517)	(890)
Recoveries	87	72	252	135
Provision (benefit)	1,096	429	1,265	755
Loans:
Loans collectively evaluated for impairment	3,076,424	1,585,981	3,076,424	1,585,981
Total loans	3,076,424	1,585,981	3,076,424	1,585,981	3,507,907
Acquired non-credit impaired loans | Consumer Owner Occupied Loans
Loans:
Total loans		221,566		221,566
Commercial non-owner occupied real estate | Non-acquired loans
Loans:
Total loans	2,042,125	1,665,153	2,042,125	1,665,153	1,839,768
Commercial non-owner occupied real estate | Non-acquired loans | Construction and land development
Allowance for loan losses:
Balance at beginning of period	5,847	4,649	5,921	4,091
Charge-offs		(69)	(35)	(474)
Recoveries	547	68	989	222
Provision (benefit)	(207)	1,098	(688)	1,907
Balance at end of period	6,187	5,746	6,187	5,746
Loans individually evaluated for impairment	846	1,310	846	1,310
Loans collectively evaluated for impairment	5,341	4,436	5,341	4,436
Loans:
Loans individually evaluated for impairment	42,392	30,037	42,392	30,037
Loans collectively evaluated for impairment	864,498	682,205	864,498	682,205
Total loans	906,890	712,242	906,890	712,242	830,875
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	6,798	5,464	6,525	4,980
Recoveries	2	7	4	48
Provision (benefit)	409	693	680	1,136
Balance at end of period	7,209	6,164	7,209	6,164
Loans individually evaluated for impairment	93	146	93	146
Loans collectively evaluated for impairment	7,116	6,018	7,116	6,018
Loans:
Loans individually evaluated for impairment	1,348	754	1,348	754
Loans collectively evaluated for impairment	1,133,887	952,157	1,133,887	952,157
Total loans	1,135,235	952,911	1,135,235	952,911	1,008,893
Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Construction and land development
Loans:
Total loans	281,282		281,282		403,357
Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate
Loans:
Loans collectively evaluated for impairment	752,465	209,560	752,465	209,560
Total loans	752,465	209,560	752,465	209,560	817,166
Commercial owner occupied real estate loan | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	8,346	7,894	8,128	8,022
Charge-offs	(81)		(81)
Recoveries	25	98	33	105
Provision (benefit)	317	(453)	527	(588)
Balance at end of period	8,607	7,539	8,607	7,539
Loans individually evaluated for impairment	44	62	44	62
Loans collectively evaluated for impairment	8,563	7,477	8,563	7,477
Loans:
Loans individually evaluated for impairment	4,750	6,054	4,750	6,054
Loans collectively evaluated for impairment	1,367,703	1,198,899	1,367,703	1,198,899
Total loans	1,372,453	1,204,953	1,372,453	1,204,953	1,262,776
Commercial owner occupied real estate loan | Non-acquired loans | Home equity loans
Allowance for loan losses:
Balance at beginning of period			3,250	3,211
Charge-offs			(71)	(224)
Recoveries			128	95
Provision (benefit)			61	165
Balance at end of period	3,368	3,247	3,368	3,247
Commercial owner occupied real estate loan | Acquired non-credit impaired loans
Loans:
Total loans	486,254		486,254		521,818
Commercial owner occupied real estate loan | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate
Allowance for loan losses:
Charge-offs			(28)
Provision (benefit)			28
Consumer real estate | Non-acquired loans
Loans:
Total loans	2,190,870	1,794,454	2,190,870	1,794,454	1,967,902
Consumer real estate | Non-acquired loans | Home equity loans
Allowance for loan losses:
Balance at beginning of period	3,237	3,456
Charge-offs	(5)	(190)
Recoveries	27	21
Provision (benefit)	109	(40)
Balance at end of period	3,368	3,247	3,368	3,247
Loans individually evaluated for impairment	180	119	180	119
Loans collectively evaluated for impairment	3,188	3,128	3,188	3,128
Loans:
Loans individually evaluated for impairment	3,144	2,626	3,144	2,626
Loans collectively evaluated for impairment	453,802	408,906	453,802	408,906
Total loans	456,946	411,532	456,946	411,532	437,642
Consumer real estate | Non-acquired loans | Consumer Owner Occupied Loans
Allowance for loan losses:
Balance at beginning of period	10,193	8,108	9,668	7,820
Charge-offs		(62)	(4)	(185)
Recoveries	41	27	64	76
Provision (benefit)	711	496	1,217	858
Balance at end of period	10,945	8,569	10,945	8,569
Loans individually evaluated for impairment	30	57	30	57
Loans collectively evaluated for impairment	10,915	8,512	10,915	8,512
Loans:
Loans individually evaluated for impairment	5,628	4,575	5,628	4,575
Loans collectively evaluated for impairment	1,728,296	1,378,347	1,728,296	1,378,347
Total loans	1,733,924	1,382,922	1,733,924	1,382,922	1,530,260
Consumer real estate | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs			(807)	(2)
Recoveries			55	2
Provision (benefit)			752
Consumer real estate | Acquired non-credit impaired loans | Home equity loans
Allowance for loan losses:
Charge-offs	(158)	(664)	(240)	(664)
Recoveries	28	60	79	69
Provision (benefit)	130	604	161	595
Loans:
Loans collectively evaluated for impairment	278,906	177,129	278,906	177,129
Total loans	278,906	177,129	278,906	177,129	320,591
Consumer real estate | Acquired non-credit impaired loans | Consumer Owner Occupied Loans
Allowance for loan losses:
Recoveries	5	2
Provision (benefit)	(5)	(305)
Loans:
Loans collectively evaluated for impairment	676,596	520,106	676,596	520,106
Total loans	676,596	520,106	676,596	520,106	710,611
Commercial and industrial | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	6,333	5,124	5,488	4,842
Charge-offs	(59)	(167)	(144)	(189)
Recoveries	199	143	214	233
Provision (benefit)	238	43	1,153	257
Balance at end of period	6,711	5,143	6,711	5,143
Loans individually evaluated for impairment	485	362	485	362
Loans collectively evaluated for impairment	6,226	4,781	6,226	4,781
Loans:
Loans individually evaluated for impairment	1,834	1,198	1,834	1,198
Loans collectively evaluated for impairment	939,233	761,385	939,233	761,385
Total loans	941,067	762,583	941,067	762,583	815,187
Commercial and industrial | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs	(764)
Recoveries	2	1
Provision (benefit)	762	(1)
Loans:
Loans collectively evaluated for impairment	304,864	117,884	304,864	117,884
Total loans	304,864	117,884	304,864	117,884	398,696
Commercial and industrial | Acquired non-credit impaired loans | Construction and land development
Loans:
Total loans		112,855		112,855
Commercial and industrial | Acquired non-credit impaired loans | Home equity loans
Loans:
Total loans		117,884		117,884
Other income producing property | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	1,393	1,345	1,375	1,542
Charge-offs		(7)		(7)
Recoveries	3	5	11	48
Provision (benefit)	17	36	27	(204)
Balance at end of period	1,413	1,379	1,413	1,379
Loans individually evaluated for impairment	144	238	144	238
Loans collectively evaluated for impairment	1,269	1,141	1,269	1,141
Loans:
Loans individually evaluated for impairment	3,240	3,641	3,240	3,641
Loans collectively evaluated for impairment	202,267	185,685	202,267	185,685
Total loans	205,507	189,326	205,507	189,326	193,847
Other income producing property | Acquired non-credit impaired loans
Allowance for loan losses:
Recoveries		1		1
Provision (benefit)		(1)		(1)
Loans:
Loans collectively evaluated for impairment	169,392	83,403	169,392	83,403
Total loans	169,392	83,403	169,392	83,403	196,669
Consumer | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	2,899	2,443	2,788	2,350
Charge-offs	(1,095)	(797)	(2,074)	(1,510)
Recoveries	207	167	410	378
Provision (benefit)	1,060	719	1,947	1,314
Balance at end of period	3,071	2,532	3,071	2,532
Loans individually evaluated for impairment	7	6	7	6
Loans collectively evaluated for impairment	3,064	2,526	3,064	2,526
Loans:
Loans individually evaluated for impairment	257	235	257	235
Loans collectively evaluated for impairment	416,393	357,526	416,393	357,526
Total loans	416,650	357,761	416,650	357,761	378,985
Consumer | Non-acquired loans | Consumer
Loans:
Total loans	416,650	357,761	416,650	357,761	378,985
Consumer | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs	(127)	(140)
Recoveries	46	7
Provision (benefit)	81	133
Loans:
Loans collectively evaluated for impairment	126,665	143,478	126,665	143,478
Total loans	126,665	143,478	126,665	143,478	137,710
Consumer | Acquired non-credit impaired loans | Consumer Owner Occupied Loans
Allowance for loan losses:
Charge-offs			(70)	(10)
Recoveries			62	42
Provision (benefit)			8	(32)
Commercial | Non-acquired loans
Loans:
Total loans	4,561,152	3,822,015	4,561,152	3,822,015	4,111,578
Commercial | Acquired non-credit impaired loans
Allowance for loan losses:
Charge-offs			(265)	(214)
Recoveries			49	19
Provision (benefit)			216	195
Commercial | Acquired non-credit impaired loans | Construction and land development
Allowance for loan losses:
Charge-offs	(106)		(107)
Recoveries	6	1	7	2
Provision (benefit)	100	(1)	100	(2)
Loans:
Loans collectively evaluated for impairment	281,282	112,855	281,282	112,855
Total loans	281,282	112,855	281,282	112,855
Commercial | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate
Allowance for loan losses:
Charge-offs	(28)
Provision (benefit)	28
Loans:
Loans collectively evaluated for impairment	486,254	221,566	486,254	221,566
Total loans	486,254	221,566	486,254	221,566
Other loans | Non-acquired loans
Allowance for loan losses:
Balance at beginning of period	157	(34)	305	102
Provision (benefit)	206	(136)	58	(272)
Balance at end of period	363	(170)	363	(170)
Loans collectively evaluated for impairment		(170)		(170)
Loans collectively evaluated for impairment	363		363
Loans:
Loans collectively evaluated for impairment	28,867	18,163	28,867	18,163
Total loans	$ 28,867	$ 18,163	$ 28,867	$ 18,163	33,690
Other loans | Acquired non-credit impaired loans
Loans:
Total loans					$ 1,289