Investment Securities (Narrative) (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Schedule of Investments [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		35.00%
Tax Equivalent Interest Adjustment		$ 2,700,000
Investment Securities average remaining life		4 years 4 months
Other than Temporary Impairment Losses, Investments	$ 0	$ 0	$ 0
Available-for-sale Securities, Gross Realized Gains	0.000	$ 0.000	$ 0.000
Asset backed securities mortgage portfolio, term		15 years
Available-for-sale Securities Pledged as Collateral	933,000,000	$ 933,000,000		$ 937,000,000
U.S. Treasury And Sponsored Entities Callable Notes [Member]
Schedule of Investments [Line Items]
Available for Sale expected to be called	0	0
Available-for-sale securities	$ 268,800,000	$ 268,800,000
U.S. Treasury And Sponsored Entities Callable Notes [Member] | Minimum [Member]
Schedule of Investments [Line Items]
Available for Sale Securities, Debt Maturities, Term		31 days
U.S. Treasury And Sponsored Entities Callable Notes [Member] | Maximum [Member]
Schedule of Investments [Line Items]
Available for Sale Securities, Debt Maturities, Term		2 years 273 days