Schedule of Outstanding Interest Rate Swaptions (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Weighted Average Months to Expiration	15 months	16 months
Options
Derivative [Line Items]
Original Cost	$ 10,813,000	$ 20,080,000
Fair Value	$ 1,831,000	$ 4,561,000
Weighted Average Months to Expiration	9 months	6 months
Underlying Swaps
Derivative [Line Items]
Notional Amount	$ 3,065,000,000	$ 992,300,000
Weighted Average Fixed Pay Rate	3.23%	2.74%
Weighted Average Term (Years)	6 years	7 years