Mortgage-Backed Securities - By Maturity (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Mortgage Backed Securities [Abstract]
Greater than five years and less than ten years	$ 1,330,000	$ 1,521,000
Greater than or equal to ten years	746,427,000	349,702,000
Total mortgage-backed securities	$ 747,757,500	$ 351,222,512