Derivative Instruments and Hedging Activities (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative net gain (loss) recognized in income statement	$ 2,716		$ (1,063)
TROR [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative net gain (loss) recognized in income statement	2,727		(1,006)
TROR [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative net gain (loss) recognized in income statement	1,408	[1]	5,354	[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	$ (11)		$ (57)

[1] The net gain (loss) recognized in interest expense from the change in fair value of the underlying TROR borrowings was $(1,408) and $(5,354) for the three months ended March 31, 2015 and 2014, respectively, offsetting the gain (loss) recognized on the TROR.