Loans - Schedule of Impaired Loans (Average Recorded Investment in Impaired Loans and Interest Income Recognized) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	$ 35,015	$ 31,348	$ 32,149	$ 34,857
Interest income recognized	645	407	1,363	1,086
Commercial
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	30,523	23,975	26,814	25,835
Interest income recognized	603	321	1,230	842
Real estate - mortgage
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	2,443	4,821	3,241	6,048
Interest income recognized	22	48	80	150
Construction and land
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	1,807	2,309	1,850	2,470
Interest income recognized	15	34	46	76
Consumer
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	242	243	244	504
Interest income recognized	5	4	7	18
Manufacturing | Commercial
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	2,444	3,100	2,173	3,815
Interest income recognized	30	31	89	122
Finance and insurance | Commercial
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	476	28	349	31
Interest income recognized	6		16
Health care | Commercial
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	500	205	432	194
Interest income recognized	15	3	29	9
Real estate services | Commercial
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	5,475	7,046	5,812	7,240
Interest income recognized	45	78	147	206
Construction | Commercial
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	1,524	1,998	1,591	1,694
Interest income recognized	39	59	79	98
Public administration | Commercial
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	106		36
Interest income recognized	1		1
Commercial - Other | Commercial
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	19,998	11,598	16,421	12,861
Interest income recognized	467	150	869	407
Residential and commercial owner-occupied | Real estate - mortgage
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	1,158	1,680	1,236	1,877
Interest income recognized	8	18	26	43
Residential and commercial investor | Real estate - mortgage
Impaired Loans: Average recorded investment and interest income
Average recorded investment in impaired loans	1,285	3,141	2,005	4,171
Interest income recognized	$ 14	$ 30	$ 54	$ 107