Loans and Allowance for Credit Losses Troubled Debt Restructurings (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	$ 66,379	$ 59,560
Non-accrual TDRs	29,051	27,850
Total TDRs	95,430	87,410
Residential Mortgage
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	26,016	27,617
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	13,959	15,957
Construction - commercial residential
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	0	726
Commercial - secured
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	10,820	6,627
Real estate – home equity
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	15,558	8,594
Consumer - direct
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	$ 26	$ 39