Derivatives and other Hedging Instruments - Additional Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Derivative [Line Items]
Estimated amount related to derivatives reclassified to interest expense during the next 12 months	$ 72,052
The weighted-average remaining term of swaps	22 months
Total fair market value of Futures Contracts	(42,967)		(25,585)
Realized loss on futures contracts	(41,615)	51
Maximum leverage ratio the Company can reach before it could be in default of one of its derivative obligations	1000.00%
Other Purchase Commitment
Derivative [Line Items]
Derivatives	1,841		(658)
Eurodollar Future
Derivative [Line Items]
Total fair market value of Futures Contracts	(42,967)		(25,585)
Notional Amount	1,000
Realized loss on futures contracts	(18,606)
Unrealized loss on futures contracts	(17,382)
Fair value of derivatives in net liability position, which includes accrued interest but excludes any adjustment for nonperformance risk, related to agreements	$ 93,429