Investment and Mortgage-Backed Securities, Available for Sale (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) security	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) security	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	$ 391,109,584		$ 391,109,584		$ 420,876,924
Available-for-sale Securities, Fair Value Disclosure	395,663,451		395,663,451		429,700,540
Available For Sale Securities Pledged as Collateral, Amortized Cost Basis	86,500,000		86,500,000		120,700,000
Available-for-sale Securities Pledged as Collateral, Fair Value	89,200,000		89,200,000		$ 124,400,000
Proceeds From Sale of Available For Sale Securities Including Mortgage Backed Securities	$ 17,900,000	$ 13,400,000	$ 54,200,000	$ 27,300,000
Percent of unrealized losses for securities in a continuous loss position for 12 months or more	9.00%		9.00%		67.80%
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	9		9		24
Available-for-sale Securities, Gross Realized Losses	$ 0	207,000	$ 47,000	432,000
GNMA Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	125,500,000		125,500,000		$ 156,800,000
Available-for-sale Securities, Fair Value Disclosure	128,400,000		128,400,000		$ 160,600,000
Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains	$ 182,000	$ 168,000	$ 1,700,000	$ 477,000