Derivative Financial Instruments - Narrative (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Eurodollar Future [Member]
Type Of Derivative Instrument [Line Items]
Underlying Risk	Interest Rate Risk	Interest Rate Risk
Description of Objective	Economically hedge a portion of interest rate risk in up-rate environment	Economically hedge a portion of interest rate risk in up-rate environment
InterestRateSwaptionMember
Type Of Derivative Instrument [Line Items]
Underlying Risk	Interest Rate Risk	Interest Rate Risk
Description of Objective	Economically hedge a portion of interest rate risk in up-rate environment	Economically hedge a portion of interest rate risk in up-rate environment
Treasury Note Future [Member]
Type Of Derivative Instrument [Line Items]
Underlying Risk	Interest Rate Risk	Interest Rate Risk
Description of Objective	Economically hedge a portion of interest rate risk in up-rate environment	Economically hedge a portion of interest rate risk in up-rate environment