Fair Value (Details)	3 Months Ended
	Mar. 31, 2017 USD ($) derivative venture	Mar. 31, 2016 USD ($)
Derivative instruments and Hedging Activities
(Loss) income on cash flow hedges	$ 145,000	$ (47,757,000)
Estimated hedging losses to be reclassified from accumulated other comprehensive loss into earnings within the next twelve months	$ 6,975,000
Cash Flow Hedges
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative	13
Interest Rate Cap [Member] | Cash Flow Hedges
Derivative instruments and Hedging Activities
Notional amount	$ 35,685,000
Weighted average interest rate (as a percent)	2.80%
Weighted average capped interest rate (as a percent)	5.90%
Interest Rate Swap [Member] | Cash Flow Hedges
Derivative instruments and Hedging Activities
Notional amount	$ 900,000,000
Weighted average capped interest rate (as a percent)	2.30%
Notional amounts entered into during period	$ 100,000,000
Put Option [Member]
Derivative instruments and Hedging Activities
Number of Ventures in which Entity is Required to Purchase Interest in Investment at Guaranteed Minimum Amount | venture	3
Not Designated as Hedging Instrument [Member]
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative	14
Not Designated as Hedging Instrument [Member] | Interest Rate Cap [Member]
Derivative instruments and Hedging Activities
Notional amount	$ 696,591,000
Weighted average interest rate (as a percent)	2.60%
Weighted average capped interest rate (as a percent)	6.10%