Commitments and Contingencies - Narrative (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($) community property Lease	Sep. 30, 2019 USD ($) community property Lease
Lessee, Lease, Description [Line Items]
Number of office leases | Lease	16	16
Operating lease assets	$ 99,270	$ 99,270
Operating lease obligation	116,489	116,489
Operating Lease, Cost	3,618	10,723
Financing lease asset	21,951	21,951
Financing lease obligation	$ 20,216	$ 20,216
Properties on Land Subject to Land Leases
Lessee, Lease, Description [Line Items]
Number of operating apartment communities owned | community	11	11
Number of operating apartment communities under construction | community	1	1
Number of commercial properties owned | property	2	2
Number of leased properties under purchase options | property		5
Assets Held under Operating Leases [Member]
Lessee, Lease, Description [Line Items]
Number of operating apartment communities owned | community	10	10
Assets Held under Finance Leases [Member]
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	2	2
Number of Finance Leases for Parking Garage Adjacent to Operating Community | Lease	1	1
Number of Finance Leases for Parking Garage Adjacent to Development Community | Lease	1	1