Derivative Financial Instruments - Narrative (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Derivitive Financial Instruments [Line Items]
Type of Derivative Instrument	Eurodollar Futures Contract	Eurodollar Futures Contract
Underlying Risk	Interest Rate Risk	Interest Rate Risk
Description of Objective	In connection with its interest rate risk management strategy, the Company economically hedges a portion of its interest rate risk by entering into derivative financial instrument contracts.