Loans and Allowance for Credit Losses Loans Modified Under Troubled Debt Restructurings (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	$ 68,886	$ 66,379
Non-accrual TDRs (1)	24,743	29,051
Total TDRs	93,629	95,430
Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	25,055	26,016
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	16,420	13,959
Real-estate - home equity
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	16,201	15,558
Commercial
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	11,199	10,820
Consumer
Financing Receivable, Modifications [Line Items]
Total Accruing Troubled Debt Restructurings	$ 11	$ 26