Investment and Mortgage-Backed Securities, Held to Maturity (Schedule of investment and mortgage-backed securities held to maturity) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, gross unrealized gains	$ 89,284
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	24,258,599
Held to maturity, gross unrealized losses	505,878
Held-to-maturity Securities, Fair Value	23,842,005	$ 27,054,934
Available-for-sale Securities, Gross Realized Losses	67,000
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities	998,214
Held to maturity, gross unrealized gains	0
Held to maturity, gross unrealized losses	25,236
Held-to-maturity Securities, Fair Value	972,978
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities	23,260,385
Held to maturity, gross unrealized gains	89,284
Held to maturity, gross unrealized losses	480,642
Held-to-maturity Securities, Fair Value	$ 22,869,027