Commitments and Contingencies - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) property Lease community	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) property Lease community	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Lessee, Lease, Description [Line Items]
Number Of Office Leases | Lease	13		13
Payments to Acquire Other Real Estate			$ 392,746	$ 0
Operating lease assets	$ 126,699		126,699		$ 133,581
Operating lease obligation	154,790		154,790		161,313
Operating Lease, Expense	3,905	$ 3,958	11,628	$ 12,115
Finance lease asset	25,616		25,616		21,685
Finance lease obligation	20,131		$ 20,131		$ 20,166
Avalon Hackensack at Riverside
Lessee, Lease, Description [Line Items]
Payments to Acquire Other Real Estate	$ 10,336
Properties on Land Subject to Land Leases
Lessee, Lease, Description [Line Items]
Number Of operating apartment communities owned | community	8		8
Number of commercial properties owned | property	2		2
Assets Held under Operating Leases
Lessee, Lease, Description [Line Items]
Number Of operating apartment communities owned | community	7		7
Assets Held under Finance Leases
Lessee, Lease, Description [Line Items]
Number Of operating apartment communities owned | community	1		1
Number Of Finance Leases For Parking Garages Adjacent To Communities | Lease	3		3