Investment and Mortgage-Backed Securities, Available for Sale (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) security	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) security	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	$ 370,462,887		$ 370,462,887		$ 369,140,098
Available-for-sale Securities, Fair Value Disclosure	380,970,307		380,970,307		375,513,870
Available For Sale Securities Pledged as Collateral, Amortized Cost Basis	71,600,000		71,600,000		81,000,000
Available-for-sale Securities Pledged as Collateral, Fair Value	74,100,000		74,100,000		$ 83,200,000
Proceeds From Sale of Available For Sale Securities Including Mortgage Backed Securities	$ 6,900,000	$ 4,000,000	$ 21,500,000	$ 58,200,000
Percent of unrealized losses for securities in a continuous loss position for 12 months or more	21.30%		21.30%		17.60%
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	13		13		9
Available-for-sale Securities, Gross Realized Losses	$ 0		$ 0	47,000
GNMA Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	112,400,000		112,400,000		$ 116,800,000
Available-for-sale Securities, Fair Value Disclosure	115,000,000		115,000,000		118,500,000
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost of Investment And Mortgage-Backed Securities Available For Sale	18,600,000		18,600,000		$ 3,800,000
Available-for-sale Securities, Fair Value Disclosure	18,300,000		18,300,000
Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains	$ 360,000	$ 8,000	$ 772,000	$ 1,700,000