Fair Value (Details) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015 USD ($) derivative	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) derivative	Sep. 30, 2014 USD ($)
Derivative instruments and Hedging Activities
Hedging losses reclassified from accumulated other comprehensive income into earnings		$ 1,342	$ 1,546	$ 4,334	$ 4,557
Estimated hedging losses to be reclassified from accumulated other comprehensive loss into earnings within the next twelve months				$ 5,493
Cash Flow Hedges
Derivative instruments and Hedging Activities
Weighted average interest rate (as a percent)	[1]	2.30%		2.30%
Number of derivative instruments held | derivative		1		1
Interest Rate Cap [Member] | Cash Flow Hedges
Derivative instruments and Hedging Activities
Notional balance		$ 36,935		$ 36,935
Weighted average capped interest rate (as a percent)		5.90%		5.90%
Not Designated as Hedging Instrument [Member]
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative		15		15
Not Designated as Hedging Instrument [Member] | Interest Rate Cap [Member]
Derivative instruments and Hedging Activities
Notional balance		$ 726,662		$ 726,662
Weighted average interest rate (as a percent)	[1]	1.80%		1.80%
Weighted average capped interest rate (as a percent)		5.80%		5.80%

[1] Represents the weighted average interest rate on the hedged debt.