Derivative Instruments and Hedging Activities (Details 2) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative net gain (loss) recognized in income statement	$ 1,635,000		$ (2,295,000)		$ 572,000		$ (1,964,000)
Total Return Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative net gain (loss) recognized in income statement	1,681,000		(2,295,000)		675,000		(1,725,000)
Total Return Swap [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative net gain (loss) recognized in income statement	(3,143,000)	[1]	257,000	[1]	2,211,000	[1]	104,000	[1]
Interest rate caps and interest rate swaps [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative net gain (loss) recognized in income statement	$ (46,000)		$ 0		$ (103,000)		$ (239,000)

[1] The net gain (loss) recognized in interest expense from the change in fair value of the underlying TRS borrowings was $3,143 and $(2,211) for the three and six months ended June 30, 2014, respectively, and $(257) and $(104) for the three and six months ended June 30, 2013, respectively, offsetting the gain (loss) recognized on the TRS.