Derivative Financial Instruments - Income Statement Effect (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	$ (5,728,196)	$ 6,851,588	$ (7,421,488)	$ 6,367,663
Eurodollar Future [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	(4,599,000)	6,852,000	(6,136,000)	6,368,000
Interest Rate Swaption [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	$ (1,129,000)	$ 0	$ (1,285,000)	$ 0