Investment Securities (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Schedule of Investments [Line Items]
Other than Temporary Impairment Losses, Investments	$ 0	$ 0
Asset backed securities mortgage portfolio, term	15 years
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Debt Securities, Available-for-sale, Amortized Cost	$ 1,139,189,000		$ 1,187,499,000
Proceeds from Sale of Available-for-sale Securities	0	$ 0
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	836,860,000		884,571,000
Collateral Pledged [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 597,000,000		$ 585,000,000