CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Supplemental disclosures of non-cash investing and financing activities
Common stock issued through the dividend reinvestment plan (in shares)	1,165	576
Common stock issued through the dividend reinvestment plan	$ 205	$ 101
Number of shares withheld to satisfy employees' tax withholding and other liabilities (in shares)	57,172	48,189
Shares withheld to satisfy employees' tax withholding and other liabilities, value	$ 10,149	$ 8,164
Stock Issued During Period, Shares, Share-based Compensation, Forfeited (in shares)	236
Stock Issued During Period, Value, Share-based Compensation, Forfeited	$ 41	76
Dividends declared but not paid	195,657	185,173
Change in redemption value of redeemable noncontrolling interest	(183)
Increase (Decrease) in Prepaid Expense and Other Assets	(180)	5,422
(Loss) income on cash flow hedges	145	(47,757)
Increase in accrued expenses, other liabilities and accrued interest payable	102	42,335
Cash flow hedge losses reclassified to earnings	1,752	1,374
Net operating real estate	15,171,803
Prepaid expenses and other assets	287,130
Avalon Maplewood [Member]
Supplemental disclosures of non-cash investing and financing activities
Net operating real estate	16,361
Prepaid expenses and other assets	$ 12,598
Mortgage notes payable | Notes Payable Maturities 2020 [Member] | Avalon Hoboken [Member]
Supplemental disclosures of non-cash investing and financing activities
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt		$ 67,904
Restricted Stock and Restricted Stock Converted From Performance Shares [Member]
Supplemental disclosures of non-cash investing and financing activities
Restricted stock granted (in shares)	198,502	193,171
Restricted Stock Converted From Performance Shares [Member]
Supplemental disclosures of non-cash investing and financing activities
Restricted stock granted (in shares)	128,482	115,618
Restricted stock
Supplemental disclosures of non-cash investing and financing activities
Restricted stock granted (in shares)	70,020	77,553
Fair value of shares issued	$ 12,538	$ 12,529
Stock Issued During Period, Shares, Share-based Compensation, Forfeited (in shares)	236	499
Retained Earnings [Member]
Supplemental disclosures of non-cash investing and financing activities
Change in redemption value of redeemable noncontrolling interest	$ (183)	$ 299