Fair Value (Details)	3 Months Ended			12 Months Ended
	Dec. 31, 2020 USD ($) derivative	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) derivative	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	May 31, 2020 USD ($)	Feb. 29, 2020 USD ($)
Derivative instruments and Hedging Activities
Derivative, Notional Amounts Settled During Period		$ 250,000,000	$ 350,000,000	$ 600,000,000
Receipts (payments) for termination of forward interest rate swaps		$ (4,821,000)	$ (20,314,000)	(25,135,000)	$ (12,309,000)	$ 12,598,000
(Loss) gain on cash flow hedges				(17,731,000)	(11,930,000)	5,132,000
Unrealized Gain (Loss) on Derivatives	$ 2,894,000			2,894,000	0	$ 0
Interest Rate Swap | Cash Flow Hedges Interest Rate Caps
Derivative instruments and Hedging Activities
Derivative, Notional Amount	$ 150,000,000			$ 150,000,000
Weighted average capped interest rate (as a percent)	0.70%			0.70%
Derivative, notional amounts entered into during period				$ 150,000,000
Interest Rate Caps
Derivative instruments and Hedging Activities
Number of derivative instruments held | derivative	10			10
Interest Rate Caps | Interest Rate Caps
Derivative instruments and Hedging Activities
Derivative, Notional Amount	$ 679,167,000			$ 679,167,000
Weighted average interest rate (as a percent)	1.70%			1.70%
Weighted average capped interest rate (as a percent)	6.40%			6.40%
Unsecured Notes 2.30 Percent [Member]
Derivative instruments and Hedging Activities
Debt Instrument, Face Amount								$ 700,000,000
Unsecured Notes 2.45 Percent [Member]
Derivative instruments and Hedging Activities
Debt Instrument, Face Amount							$ 600,000,000
Reclassification out of Accumulated Other Comprehensive Income
Derivative instruments and Hedging Activities
Gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred				$ 9,467,000
Avalon Brooklyn Bay
Derivative instruments and Hedging Activities
Due from Related Parties	$ 3,645,000			$ 3,645,000	$ 10,650,000