Real Estate Disposition Activities (Details) ft² in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) ft² home residential_condominium community	Dec. 31, 2019 USD ($) home	Dec. 31, 2018 USD ($) home
Summary of income from discontinued operations
Gain on sale of communities	$ 340,444	$ 166,105	$ 374,976
Number of communities held for sale | community	1
Gain (Loss) on Sale of Other Investments	$ 8,213	0	0
Other Selling, General and Administrative Expense	5,662	3,812	1,044
Inventory, Real Estate	267,219	457,809
Income Tax Expense (Benefit)	$ (3,247)	$ 13,003	$ (160)
Number of Residential Condominiums Sold | residential_condominium	70
Number of Residential Condominiums Remaining to be Sold | residential_condominium	102
Avalon Shelton [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home	250
Gross sales price	$ 64,750
Net cash proceeds	$ 63,030
Avalon Tinton Falls [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home	216
Gross sales price	$ 64,900
Net cash proceeds	$ 63,371
Avalon Towers [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home	109
Gross sales price	$ 54,000
Net cash proceeds	$ 53,079
Avalon Somerset [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home	384
Gross sales price	$ 110,000
Net cash proceeds	$ 107,415
Eaves San Rafael [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home	254
Gross sales price	$ 106,000
Net cash proceeds	$ 104,462
Avalon Cohasset [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home	220
Gross sales price	$ 90,250
Net cash proceeds	$ 88,673
Avalon Wilton on Danbury Rd [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home	100
Gross sales price	$ 34,750
Net cash proceeds	$ 33,744
Avalon at Stratford [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home	130
Gross sales price	$ 30,600
Net cash proceeds	$ 29,808
Eaves Diamond Heights [Member]
Summary of income from discontinued operations
Number Of Apartment Homes Sold | home	154
Gross sales price	$ 72,500
Net cash proceeds	69,469
Other Real Estate Sales
Summary of income from discontinued operations
Gross sales price	6,500
Net cash proceeds	$ 6,722
Wholly Owned Properties
Summary of income from discontinued operations
Number of apartment communities sold | community	9
Number Of Apartment Homes Sold | home	1,817	1,660	3,099
Sale of communities gross sales price	$ 627,750
Gain on sale of communities	340,444
Gross sales price	634,250	$ 431,280	$ 1,378,289
Net cash proceeds	619,773	422,041	883,313
Repayments of secured debt		21,700	$ 395,939
The Park Loggia [Member]
Summary of income from discontinued operations
Net cash proceeds	$ 216,372
Number of residential units in development | residential_condominium	172
Retail square feet development | ft²	66
Gain (Loss) on Sale of Other Investments	$ 8,213
Income Tax Expense (Benefit)		$ 5,782,000