Fair Value (Details)	3 Months Ended					9 Months Ended
	Sep. 30, 2019 USD ($) derivative	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2019 USD ($) derivative venture	Sep. 30, 2018 USD ($)
Derivative instruments and Hedging Activities
Derivative, Notional Amounts Settled During Period						$ 250,000,000
Payments for (Proceeds from) Hedge, Financing Activities						$ 12,309,000	$ (12,598,000)
Amortization Period of Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge						10 years
(Loss) gain on cash flow hedges	$ (13,644,000)	$ (2,888,000)	$ (7,231,000)	$ 0	$ 11,501,000	$ (23,763,000)	$ 11,499,000
Cash Flow Hedges
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative	6					6
Interest Rate Swap | Cash Flow Hedges
Derivative instruments and Hedging Activities
Derivative, Notional Amounts Entered into During Period	$ 100,000,000					$ 350,000,000
Derivative, Notional Amount	$ 350,000,000					$ 350,000,000
Put Option
Derivative instruments and Hedging Activities
Number of ventures in which entity is required to purchase interest in investment at guaranteed minimum amount | venture						2
Reclassification out of Accumulated Other Comprehensive Income
Derivative instruments and Hedging Activities
Estimated hedging losses to be reclassified from accumulated other comprehensive loss into earnings within the next twelve months						$ 6,983,000
Not Designated as Hedging Instrument
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative	5					5
Not Designated as Hedging Instrument | Interest Rate Cap
Derivative instruments and Hedging Activities
Derivative, Notional Amount	$ 445,015,000					$ 445,015,000
Unsecured notes | Unsecured Notes 3.30 Percent [Domain]
Derivative instruments and Hedging Activities
Debt Instrument, Interest Rate, Stated Percentage		3.30%