CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical)	12 Months Ended
	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) home shares	Dec. 31, 2015 USD ($) shares
Supplemental disclosures of non-cash investing and financing activities
Common stock issued through the dividend reinvestment plan (in shares) | shares	3,058	2,396	2,142
Common stock issued through the dividend reinvestment plan	$ 558,000	$ 424,000	$ 372,000
Number of shares withheld to satisfy employees' tax withholding and other liabilities | shares	60,319	53,453	45,090
Shares withheld to satisfy employees' tax withholding and other liabilities, value	$ 10,542,000	$ 8,356,000	$ 5,979,000
Number of shares forfeited | shares	3,388
Shares cancelled upon forfeiture	$ 588,000	694,000	726,000
Common stock dividends declared but not paid	196,094,000	185,397,000	171,257,000
Change in redemption value of redeemable noncontrolling interest	(2,026,000)	(1,489,000)	(965,000)
Increase (decrease) in derivative assets	(12,114,000)	12,085,000
Increase (decrease) in derivative liabilities	1,171,000
Cash flow hedge losses reclassified to earnings	7,070,000	6,433,000	5,774,000
Net operating real estate	16,342,893,000	15,045,593,000
Income (loss) on cash flow hedges	(13,979,000)	(5,556,000)	5,354,000
Casualty and impairment loss (gain), net	$ 6,250,000	$ (3,935,000)	$ (10,542,000)
Restricted Stock and Restricted Stock Converted From Performance Shares [Member]
Supplemental disclosures of non-cash investing and financing activities
Granted (in shares) | shares	201,824	197,018	157,779
Restricted Stock Converted From Performance Shares [Member]
Supplemental disclosures of non-cash investing and financing activities
Granted (in shares) | shares	128,482	115,618	95,826
Restricted stock
Supplemental disclosures of non-cash investing and financing activities
Granted (in shares) | shares	73,342	81,400	61,953
Fair value of shares issued	$ 13,171,000	$ 13,217,000	$ 10,720,000
Number of shares forfeited | shares	3,388	4,262	1,529
Accumulated earnings less dividends
Supplemental disclosures of non-cash investing and financing activities
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	$ 65,000
Change in redemption value of redeemable noncontrolling interest	(2,026,000)	$ (1,489,000)	$ (2,053,000)
Deferred Compensation, Share-based Payments [Member] | Non Employee Director [Member]
Supplemental disclosures of non-cash investing and financing activities
Fair value of shares issued		3,894,000	3,552,000
Avalon Maplewood [Member]
Supplemental disclosures of non-cash investing and financing activities
Net operating real estate	16,361,000
Casualty and impairment loss (gain), net	$ 2,338,000
Avalon at Edgewater [Member]
Supplemental disclosures of non-cash investing and financing activities
Net operating real estate			21,844,000
Casualty and impairment loss (gain), net		$ (8,702,000)	(15,538,000)
New England [Member]
Supplemental disclosures of non-cash investing and financing activities
Casualty and impairment loss (gain), net			4,195,000
New England [Member] | Avalon at Edgewater [Member]
Supplemental disclosures of non-cash investing and financing activities
Casualty and impairment loss (gain), net			$ 26,039,000
Non Employee Director [Member] | Deferred Compensation, Share-based Payments [Member]
Supplemental disclosures of non-cash investing and financing activities
Granted (in shares) | shares		44,327	46,589
Secured notes | Notes Payable Maturities 2020 [Member] | 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 [Member] | Avalon Columbia Pike [Member]
Supplemental disclosures of non-cash investing and financing activities
Assumed principal amount of indebtedness		$ 70,507,000
West Hollywood Affordable [Member]
Supplemental disclosures of non-cash investing and financing activities
Apartment homes | home		77
Accounts receivable, net		$ 18,643,000