Derivative Financial Instruments - Narrative (Details)	6 Months Ended
	Jun. 30, 2015
Eurodollar Future [Member]
Type Of Derivative Instrument [Line Items]
Underlying Risk	Interest Rate Risk
Description of Objective	Economically hedge a portion of interest rate risk in up-rate environment
InterestRateSwaptionMember
Type Of Derivative Instrument [Line Items]
Underlying Risk	Interest Rate Risk
Description of Objective	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
Description of Objective	Economically hedge a portion of interest rate risk in up-rate environment