Investment Securities (Narrative) (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Schedule of Investments [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%
Investment Securities average remaining life		4 years 9 months 26 days
Available-for-sale Securities, Gross Realized Losses		$ 2,600,000
Debt securities held-to-maturity, at amortized cost (fair value of $344,341 and $363,779 at September 30, 2018 and December 31, 2017, respectively)	$ 350,642,000	350,642,000		$ 357,197,000
Debt Securities, Held-to-maturity, Sold, Realized Gain (Loss)		$ 291,000
percent of held to securities sold paid down	96.30%	96.30%
Other than Temporary Impairment Losses, Investments	$ 0	$ 0	$ 0
Available-for-sale Securities, Gross Realized Gains			$ 0.000
Asset backed securities mortgage portfolio, term		15 years
Available-for-sale securities	1,074,605,000	$ 1,074,605,000		1,097,645,000
Securities sold at a gain [Member]
Schedule of Investments [Line Items]
Available-for-sale securities	246,961,000	246,961,000
Securities sold at a gain [Member]
Schedule of Investments [Line Items]
Debt securities held-to-maturity, at amortized cost (fair value of $344,341 and $363,779 at September 30, 2018 and December 31, 2017, respectively)	7,400,000	7,400,000
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt securities held-to-maturity, at amortized cost (fair value of $344,341 and $363,779 at September 30, 2018 and December 31, 2017, respectively)	46,974,000	46,974,000		56,785,000
Collateral Pledged [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 564,000,000	$ 564,000,000		$ 557,000,000