CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical)	12 Months Ended
	Dec. 31, 2018 USD ($) home shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) home shares
Supplemental disclosures of non-cash investing and financing activities
Common stock issued through the dividend reinvestment plan (in shares) | shares	2,272	3,058	2,396
Common stock issued through the dividend reinvestment plan	$ 387,000	$ 558,000	$ 424,000
Number of shares withheld to satisfy employees' tax withholding and other liabilities | shares	68,565	60,319	53,453
Shares withheld to satisfy employees' tax withholding and other liabilities, value	$ 10,556,000	$ 10,542,000	$ 8,356,000
Number of shares forfeited | shares	4,860
Shares cancelled upon forfeiture	$ 717,000	588,000	694,000
Common stock dividends declared but not paid	204,191,000	196,094,000	185,397,000
Change in redemption value of redeemable noncontrolling interest	(223,000)	(2,026,000)	(1,489,000)
Increase (decrease) in derivative liabilities	(6,366,000)	1,171,000
Cash flow hedge losses reclassified to earnings	(6,143,000)	(7,070,000)	(6,433,000)
Investments in unconsolidated real estate entities	217,432,000	163,475,000
Increase (decrease) in derivative assets		12,114,000	$ 12,085,000
Net operating real estate	$ 15,822,878,000	$ 16,342,893,000
Restricted Stock and Restricted Stock Converted From Performance Shares
Supplemental disclosures of non-cash investing and financing activities
Granted (in shares) | shares	187,010	201,824	197,018
Restricted Stock Converted From Performance Shares [Member]
Supplemental disclosures of non-cash investing and financing activities
Granted (in shares) | shares	88,297	128,482	115,618
Restricted stock
Supplemental disclosures of non-cash investing and financing activities
Granted (in shares) | shares	98,713	73,342	81,400
Fair value of shares issued	$ 15,950,000	$ 13,171,000	$ 13,217,000
Number of shares forfeited | shares	4,860	3,388	4,262
Accumulated earnings less dividends
Supplemental disclosures of non-cash investing and financing activities
Change in redemption value of redeemable noncontrolling interest	$ (223,000)	$ (2,026,000)	$ (1,489,000)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests		65,000
Deferred Compensation, Share-based Payments [Member] | Non-employee directors
Supplemental disclosures of non-cash investing and financing activities
Fair value of shares issued			$ 3,894,000
Avalon Maplewood
Supplemental disclosures of non-cash investing and financing activities
Net operating real estate		$ 16,361,000
Non-employee directors | Deferred Compensation, Share-based Payments [Member]
Supplemental disclosures of non-cash investing and financing activities
Granted (in shares) | shares			44,327
Secured notes | Notes Payable Maturities 2020 | Avalon Hoboken [Member]
Supplemental disclosures of non-cash investing and financing activities
Assumed principal amount of indebtedness			$ 67,904,000
Secured notes | Notes Payable Maturities 2020 | Avalon Columbia Pike [Member]
Supplemental disclosures of non-cash investing and financing activities
Assumed principal amount of indebtedness			$ 70,507,000
NYC JV
Supplemental disclosures of non-cash investing and financing activities
Repayments of secured debt	$ 395,939,000
Apartment homes | home	1,301
West Hollywood Affordable [Member]
Supplemental disclosures of non-cash investing and financing activities
Apartment homes | home			77
Accounts receivable, net			$ 18,643,000
NYC JV
Supplemental disclosures of non-cash investing and financing activities
Investments in unconsolidated real estate entities	$ 74,159,000
Equity Method Investment, Ownership Percentage	20.00%