CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) shares	Jun. 30, 2016 USD ($) shares
Supplemental disclosures of non-cash investing and financing activities
Common stock issued through the dividend reinvestment plan (in shares) | shares		1,828	1,041
Common stock issued through the dividend reinvestment plan		$ 331	$ 186
Number of shares withheld to satisfy employees' tax withholding and other liabilities (in shares) | shares		59,019	53,011
Shares withheld to satisfy employees' tax withholding and other liabilities, value		$ 10,496	$ 8,280
Stock issued during period, shares, share-based compensation, forfeited (in shares) | shares		2,211
Stock Issued During Period, Value, Share-based Compensation, Forfeited		$ 381	360
Dividends declared but not paid	$ 185,369	196,079	185,369
Change in redemption value of redeemable noncontrolling interest		(397)
Increase (Decrease) in Prepaid Expense and Other Assets		674	(2,689)
Loss on cash flow hedges	(26,788)	(16,013)	(74,545)
Increase in accrued expenses, other liabilities and accrued interest payable		1,612	54,311
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			57,000
Cash flow hedge losses reclassified to earnings	1,561	3,534	2,935
Net operating real estate		15,297,364
Prepaid expenses and other assets		266,909
Avalon Maplewood
Supplemental disclosures of non-cash investing and financing activities
Net operating real estate		16,361
Prepaid expenses and other assets		$ 10,951
Mortgage notes payable | Notes Payable Maturities 2020 | 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		$ 67,904
Restricted Stock and Restricted Stock Converted From Performance Shares
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares		201,314	196,059
Restricted Stock Converted From Performance Shares
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares		128,482	115,618
Restricted stock
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares		72,832	80,441
Fair value of shares issued		$ 13,079	$ 13,049
Stock issued during period, shares, share-based compensation, forfeited (in shares) | shares		2,211	2,243
Retained Earnings [Member]
Supplemental disclosures of non-cash investing and financing activities
Change in redemption value of redeemable noncontrolling interest		$ (397)	$ 375
Deferred Compensation, Share-based Payments [Member] | Non Employee Director
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares) | shares			44,327
Non Employee Director | Deferred Compensation, Share-based Payments [Member]
Supplemental disclosures of non-cash investing and financing activities
Fair value of shares issued			$ 3,894