Real Estate Disposition Activities (Details) ft² in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) community home ft² land_parcel	Dec. 31, 2018 USD ($) home	Dec. 31, 2017 USD ($) home
Summary of income from discontinued operations
Gain on sale of communities		$ 166,105	$ 374,976	$ 252,599
Gain (loss) on other real estate transactions, net		439	345	(10,907)
Other Selling, General and Administrative Expense		$ 3,812	1,044	0
Number of land parcels sold | land_parcel		2
Number of communities held for sale | community		1
Inventory, Real Estate		$ 457,809	0
Income Tax Expense (Benefit)		$ 13,003	$ (160)	$ 141
Oakwood Arlington [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		184
Gross sales price		$ 70,000
Net cash proceeds		$ 68,317
Archstone Toscano
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		474
Gross sales price		$ 98,000
Net cash proceeds		$ 95,975
AVA Stamford [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		306
Gross sales price		$ 105,000
Net cash proceeds		$ 102,485
Archstone Lexington [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		222
Gross sales price		$ 45,100
Net cash proceeds		$ 44,524
Memorial Heights Villages
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		318
Gross sales price		$ 65,250
Net cash proceeds		$ 63,298
Avalon Orchards [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home		156
Gross sales price		$ 44,250
Net cash proceeds		43,448
Other Real Estate Sales
Summary of income from discontinued operations
Gross sales price		3,680
Gain (loss) on other real estate transactions, net		439
Net cash proceeds		$ 3,995
Wholly Owned Properties
Summary of income from discontinued operations
Number of apartment communities sold | community		6
Number Of Apartment Homes Sold | home		1,660	3,099	1,624
Sale of communities gross sales price		$ 427,600
Gain on sale of communities		166,105
Gross sales price		431,280	$ 1,378,289	$ 514,654
Repayments of secured debt		21,700	395,939	0
Net cash proceeds		$ 422,042	$ 883,313	$ 503,039
The Park Loggia [Member] | Development Communities
Summary of income from discontinued operations
Number of residential units in development | home		172
Retail square feet development | ft²		67
Real Estate Investments, Projected Total Capitalized Cost		$ 626,000
Income Tax Expense (Benefit)		$ 5,782
Secured notes | Notes Payable Maturities 2020 | Archstone Lexington [Member]
Summary of income from discontinued operations
Repayments of secured debt	$ 21,700