Fair Value (Details) $ in Thousands	1 Months Ended	12 Months Ended
	May. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) derivative	Dec. 31, 2014 USD ($) item	Dec. 31, 2013 USD ($)
Derivative instruments and Hedging Activities
Notional balance			$ 215,000
Hedging losses reclassified from accumulated other comprehensive income into earnings		$ 5,774	6,237	$ 59,376
Charge for the reversal of the deferred loss			51,000
Estimated hedging losses to be reclassified from accumulated other comprehensive loss into earnings within the next twelve months		$ (5,493)
Payment for settlement of forward starting interest rate swap agreement	$ 51,000
Cash Flow Hedges Interest Rate Caps
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative		10
Amount of (decrease) increase in comprehensive loss to adjust hedging derivatives		$ (11,128)	$ (6,116)	$ 5,892
Cash Flow Hedges Interest Rate Caps | Interest Rate Caps
Derivative instruments and Hedging Activities
Notional balance		$ 36,731
Weighted average interest rate (as a percent)		2.70%
Weighted average capped interest rate (as a percent)		5.90%
Cash Flow Hedges Interest Rate Caps | Interest Rate Swap [Member]
Derivative instruments and Hedging Activities
Notional balance		$ 600,000
Weighted average capped interest rate (as a percent)		2.30%
Puts
Derivative instruments and Hedging Activities
Number of ventures in which entity is required to purchase interest in investment at guaranteed minimum amount | item			3
Non-designated Hedges Interest Rate Caps
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative		15
Non-designated Hedges Interest Rate Caps | Interest Rate Caps
Derivative instruments and Hedging Activities
Notional balance		$ 725,832
Weighted average interest rate (as a percent)		1.80%
Weighted average capped interest rate (as a percent)		5.80%