Loans and Allowance for Credit Losses Loans Modified Under Troubled Debt Restructurings (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	$ 67,058	$ 66,379
Non-accrual TDRs (1)	23,238	29,051
Total TDRs	90,296	95,430
Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	24,810	26,016
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	15,690	13,959
Real-estate - home equity
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	16,208	15,558
Commercial
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	10,342	10,820
Consumer
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	$ 8	$ 26