Investment and Mortgage-Backed Securities, Available for Sale (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014 security	Sep. 30, 2013	Sep. 30, 2014 security	Sep. 30, 2013	Dec. 31, 2013 security
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains	$ 319,000	$ 520,000	$ 795,000	$ 1,300,000
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	421,262,865		421,262,865		430,241,854
Available-for-sale Securities, Fair Value Disclosure	428,819,911		428,819,911		431,003,452
Available For Sale Securities Pledged as Collateral, Amortized Cost Basis	125,700,000		125,700,000		118,300,000
Available-for-sale Securities Pledged as Collateral, Fair Value	129,100,000		129,100,000		121,100,000
Percent of unrealized losses for securities in a continuous loss position for 12 months or more	11.30%		11.30%		11.40%
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	22		22		11
Available-for-sale Securities, Gross Realized Losses	176,000	101,000	607,000	101,000
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	27,300,000	17,100,000	54,600,000	48,900,000
GNMA Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	162,200,000		162,200,000		170,400,000
Available-for-sale Securities, Fair Value Disclosure	$ 166,200,000		$ 166,200,000		$ 173,500,000