Loans, Troubled Debt Restructurings Performing and Nonaccrual (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	$ 74,618	$ 79,857	$ 87,363
Nonaccrual Restructured Loans	23,486	29,385	37,684
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	30,047	31,884	29,293
Nonaccrual Restructured Loans	1,776	1,276	1,714
Commercial real estate — owner occupied
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	3,989	5,490	7,877
Nonaccrual Restructured Loans	0	2,220	2,703
Commercial real estate — investor
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	14,389	15,289	21,915
Nonaccrual Restructured Loans	0	924	3,936
Real estate construction
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	310	359	510
Nonaccrual Restructured Loans	157	150	177
Residential mortgage
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	17,068	18,100	19,870
Nonaccrual Restructured Loans	18,991	21,906	24,592
Home equity
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	7,705	7,756	7,069
Nonaccrual Restructured Loans	2,537	2,877	4,522
Other consumer
Financing Receivable, Modifications [Line Items]
Performing Restructured Loans	1,110	979	829
Nonaccrual Restructured Loans	$ 25	$ 32	$ 40