Investment and Mortgage-Backed Securities, Held to Maturity (Schedule of Held-to-maturity Securities) (Details)	6 Months Ended
	Jun. 30, 2017 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 10,637,052
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss	40,207
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	40,207
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	10,637,052
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	7,640,170
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss	37,089
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	37,089
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	$ 7,640,170