Fair Value (Details)	3 Months Ended				6 Months Ended
	Jun. 30, 2020 USD ($) derivative	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jun. 30, 2020 USD ($) venture derivative	Jun. 30, 2019 USD ($)
Derivative instruments and Hedging Activities
Derivative, Notional Amounts Settled During Period	$ 250,000,000	$ 350,000,000			$ 600,000,000
Payments for (Proceeds from) Hedge, Financing Activities	4,821,000	20,314,000			25,135,000	$ 12,309,000
Loss on cash flow hedges	$ (1,461,000)	(17,603,000)	$ (2,888,000)	$ (7,231,000)	$ (19,064,000)	$ (10,119,000)
Cash Flow Hedges
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative	2				2
Interest Rate Swap | Cash Flow Hedges
Derivative instruments and Hedging Activities
Derivative, Notional Amounts Entered into During Period					$ 100,000,000
Derivative, Notional Amount	$ 100,000,000				$ 100,000,000
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					$ 9,467,000
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	$ 441,368,000				$ 441,368,000
Unsecured Notes 2.45 Percent [Member]
Derivative instruments and Hedging Activities
Debt Instrument, Face Amount	$ 600,000,000				$ 600,000,000
Unsecured Notes 2.30 Percent [Member]
Derivative instruments and Hedging Activities
Debt Instrument, Face Amount		$ 700,000,000