Loans and Allowance for Loan Losses - Nonaccrual loans - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Non acquired non-accrual loans
Loans and Allowance for Loan Losses
Nonaccrual loans	$ 15,279	$ 12,367	$ 15,279	$ 12,367	$ 14,340
Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20
Loans and Allowance for Loan Losses
Unpaid Contractual Principal Balance	57,156	74,409	57,156	74,409	77,648
Recorded Investment With No Allowance	10,747	7,182	10,747	7,182	10,985
Gross Recorded Investment With Allowance	43,893	53,610	43,893	53,610	52,438
Total Recorded Investment	54,640	60,792	54,640	60,792	63,423
Related Allowance	1,657	1,862	1,657	1,862	1,624
Average Investment In Impaired Loans	58,617	54,955	59,032	41,002
Interest Income Recognized	346	677	1,593	1,396
Acquired non-credit impaired non-accrual including restructured loans
Loans and Allowance for Loan Losses
Nonaccrual loans	10,798	5,457	10,798	5,457	9,397
Commercial non-owner occupied real estate | Non acquired non-accrual loans
Loans and Allowance for Loan Losses
Nonaccrual loans	1,514	2,812	1,514	2,812	2,886
Commercial non-owner occupied real estate | Non acquired non-accrual loans | Construction and land development
Loans and Allowance for Loan Losses
Nonaccrual loans	404	57	404	57	251
Commercial non-owner occupied real estate | Non acquired non-accrual loans | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Nonaccrual loans	1,110	2,755	1,110	2,755	2,635
Commercial non-owner occupied real estate | Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20 | Construction and land development
Loans and Allowance for Loan Losses
Unpaid Contractual Principal Balance	36,203	46,664	36,203	46,664	47,553
Recorded Investment With No Allowance	1,029	954	1,029	954	649
Gross Recorded Investment With Allowance	34,747	41,684	34,747	41,684	42,581
Total Recorded Investment	35,776	42,638	35,776	42,638	43,230
Related Allowance	723	1,266	723	1,266	1,063
Average Investment In Impaired Loans	39,084	36,337	39,503	22,835
Interest Income Recognized	158	486	968	800
Commercial non-owner occupied real estate | Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20 | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Unpaid Contractual Principal Balance	1,480	2,361	1,480	2,361	3,106
Recorded Investment With No Allowance	812	207	812	207	860
Gross Recorded Investment With Allowance	503	509	503	509	515
Total Recorded Investment	1,315	716	1,315	716	1,375
Related Allowance	81	133	81	133	125
Average Investment In Impaired Loans	1,332	735	1,345	761
Interest Income Recognized	5	3	19	15
Commercial non-owner occupied real estate | Acquired non-credit impaired non-accrual including restructured loans
Loans and Allowance for Loan Losses
Nonaccrual loans	402	233	402	233	108
Commercial non-owner occupied real estate | Acquired non-credit impaired non-accrual including restructured loans | Construction and land development
Loans and Allowance for Loan Losses
Nonaccrual loans	402	233	402	233	108
Commercial owner occupied real estate loan | Non acquired non-accrual loans
Loans and Allowance for Loan Losses
Nonaccrual loans	1,063	557	1,063	557	1,144
Commercial owner occupied real estate loan | Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20
Loans and Allowance for Loan Losses
Unpaid Contractual Principal Balance	5,507	9,504	5,507	9,504	9,212
Recorded Investment With No Allowance	2,668	3,936	2,668	3,936	3,553
Gross Recorded Investment With Allowance	1,883	1,938	1,883	1,938	2,089
Total Recorded Investment	4,551	5,874	4,551	5,874	5,642
Related Allowance	40	64	40	64	64
Average Investment In Impaired Loans	4,650	5,964	5,096	6,060
Interest Income Recognized	81	63	228	208
Commercial owner occupied real estate loan | Acquired non-credit impaired non-accrual including restructured loans
Loans and Allowance for Loan Losses
Nonaccrual loans	904		904		189
Consumer loans | Non acquired non-accrual loans
Loans and Allowance for Loan Losses
Nonaccrual loans	9,029	3,982	9,029	3,982	5,157
Consumer loans | Non acquired non-accrual loans | Home equity loans
Loans and Allowance for Loan Losses
Nonaccrual loans	2,623	308	2,623	308	269
Consumer loans | Non acquired non-accrual loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Nonaccrual loans	6,406	3,674	6,406	3,674	4,888
Consumer loans | Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20
Loans and Allowance for Loan Losses
Average Investment In Impaired Loans			226	200
Interest Income Recognized				5
Consumer loans | Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20 | Home equity loans
Loans and Allowance for Loan Losses
Unpaid Contractual Principal Balance	3,141	3,184	3,141	3,184	3,602
Recorded Investment With No Allowance	1,135	716	1,135	716	896
Gross Recorded Investment With Allowance	1,891	1,907	1,891	1,907	2,115
Total Recorded Investment	3,026	2,623	3,026	2,623	3,011
Related Allowance	171	116	171	116	135
Average Investment In Impaired Loans	3,085	2,624	3,019	2,148
Interest Income Recognized	30	29	95	75
Consumer loans | Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20 | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Unpaid Contractual Principal Balance	5,914	5,986	5,914	5,986	7,382
Recorded Investment With No Allowance	4,478	1,369	4,478	1,369	4,392
Gross Recorded Investment With Allowance	942	3,086	942	3,086	1,240
Total Recorded Investment	5,420	4,455	5,420	4,455	5,632
Related Allowance	28	47	28	47	37
Average Investment In Impaired Loans	5,524	4,515	5,527	5,064
Interest Income Recognized	32	36	120	110
Consumer loans | Acquired non-credit impaired non-accrual including restructured loans
Loans and Allowance for Loan Losses
Nonaccrual loans	7,309	3,704	7,309	3,704	6,745
Consumer loans | Acquired non-credit impaired non-accrual including restructured loans | Home equity loans
Loans and Allowance for Loan Losses
Nonaccrual loans	4,901	1,813	4,901	1,813	4,589
Consumer loans | Acquired non-credit impaired non-accrual including restructured loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Nonaccrual loans	2,408	1,891	2,408	1,891	2,156
Commercial and industrial | Non acquired non-accrual loans
Loans and Allowance for Loan Losses
Nonaccrual loans	957	1,952	957	1,952	1,662
Commercial and industrial | Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20
Loans and Allowance for Loan Losses
Unpaid Contractual Principal Balance	1,462	1,753	1,462	1,753	2,246
Recorded Investment With No Allowance	467		467		635
Gross Recorded Investment With Allowance	942	627	942	627	521
Total Recorded Investment	1,409	627	1,409	627	1,156
Related Allowance	475	18	475	18	15
Average Investment In Impaired Loans	1,622	912	1,282	945
Interest Income Recognized	8	8	43	30
Commercial and industrial | Acquired non-credit impaired non-accrual including restructured loans
Loans and Allowance for Loan Losses
Nonaccrual loans	354	114	354	114	133
Other income producing property | Non acquired non-accrual loans
Loans and Allowance for Loan Losses
Nonaccrual loans	474	1,083	474	1,083	764
Other income producing property | Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20
Loans and Allowance for Loan Losses
Unpaid Contractual Principal Balance	3,165	4,334	3,165	4,334	3,893
Recorded Investment With No Allowance	158		158
Gross Recorded Investment With Allowance	2,772	3,605	2,772	3,605	3,138
Total Recorded Investment	2,930	3,605	2,930	3,605	3,138
Related Allowance	133	211	133	211	178
Average Investment In Impaired Loans	3,085	3,623	3,034	2,989
Interest Income Recognized	32	50	120	153
Other income producing property | Acquired non-credit impaired non-accrual including restructured loans
Loans and Allowance for Loan Losses
Nonaccrual loans	249	107	249	107	316
Consumer | Non acquired non-accrual loans
Loans and Allowance for Loan Losses
Nonaccrual loans	1,177	1,123	1,177	1,123	1,802
Consumer | Impaired non-acquired and acquired loans accounted under FASB ASC topic 310-20
Loans and Allowance for Loan Losses
Unpaid Contractual Principal Balance	284	623	284	623	654
Gross Recorded Investment With Allowance	213	254	213	254	239
Total Recorded Investment	213	254	213	254	239
Related Allowance	6	7	6	7	7
Average Investment In Impaired Loans	235	245
Interest Income Recognized		2
Consumer | Acquired non-credit impaired non-accrual including restructured loans
Loans and Allowance for Loan Losses
Nonaccrual loans	1,580	1,299	$ 1,580	1,299	1,906
Restructured loans | ASC Topic 31020 Loans
Loans and Allowance for Loan Losses
Number of months generally required to return to accruing status			6 months
Restructured loans | Non acquired non-accrual loans
Loans and Allowance for Loan Losses
Nonaccrual loans	$ 1,065	$ 858	$ 1,065	$ 858	$ 925