Mortgage-Backed Securities - By Maturity (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Mortgage Backed Securities By Maturity [Abstract]
Less than one year	$ 0	$ 0
Greater than one year and less than five years	89,000	163,000
Greater than five years and less than ten years	11,819,000	12,980,000
Greater than or equal to ten years	368,652,000	155,012,000
Total mortgage-backed securities	$ 380,559,808	$ 168,155,007