Fair Value (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2016 USD ($) derivative	Mar. 31, 2015 USD ($)
Derivative instruments and Hedging Activities
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		$ (1,374)	$ (1,595)
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion		1,374	$ 1,565
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]	2.70%
Number of derivative instruments held | derivative		16
Interest Rate Cap [Member] | Cash Flow Hedges
Derivative instruments and Hedging Activities
Notional amount		$ 36,525
Weighted average capped interest rate (as a percent)		5.90%
Interest Rate Swap [Member] | Cash Flow Hedges
Derivative instruments and Hedging Activities
Notional amount		$ 1,050,000
Weighted average capped interest rate (as a percent)		2.30%
Notional amounts entered into during period		$ 450,000
Not Designated as Hedging Instrument [Member]
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative		15
Not Designated as Hedging Instrument [Member] | Interest Rate Cap [Member]
Derivative instruments and Hedging Activities
Notional amount		$ 724,700
Weighted average interest rate (as a percent)	[1]	1.90%
Weighted average capped interest rate (as a percent)		5.80%

[1] (1)For interest rate caps, represents the weighted average interest rate on the hedged debt.