CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($)	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Supplemental disclosures of non-cash investing and financing activities
Stock issued in connection with stock grants (in shares)	157,779	113,822
Common stock issued through the dividend reinvestment plan (in shares)	1,028	1,286
Common stock issued through the dividend reinvestment plan	$ 177,000	$ 165,000
Number of shares withheld to satisfy employees' tax withholding and other liabilities	36,104	50,105
Shares withheld to satisfy employees' tax withholding and other liabilities, value	$ 5,793,000	$ 4,689,000
Stock Issued During Period, Shares, Share-based Compensation, Forfeited	2,011
Forward Contract Indexed to Issuer's Equity, Shares	609,275
Stock Issued During Period, Value, Share-based Compensation, Forfeited	$ 226,000	1,284,000
Casualty Loss	13,495,510,000
Dividends declared but not paid	166,113,000	152,113,000
(Decrease) increase in redeemable noncontrolling interests	(1,807,000)	626,000
Cash flow hedge losses reclassified to earnings	$ 2,992,000	3,011,000
Noncontrolling Interest, Decrease from Deconsolidation		$ 17,816,000
Restricted stock
Supplemental disclosures of non-cash investing and financing activities
Conversion of restricted stock units (in shares)	95,826	16,193
Restricted stock granted (in shares)	61,953	97,629
Fair value of shares issued	$ 10,721,000	$ 12,607,000
Avalon at Edgewater [Member]
Supplemental disclosures of non-cash investing and financing activities
Insurance Proceeds	44,142,000
Casualty Loss	$ 21,844,000
Deferred Compensation, Share-based Payments [Member] | Non Employee Director [Member]
Supplemental disclosures of non-cash investing and financing activities
Conversion of restricted stock units (in shares)	46,589
Fair value of shares issued	$ 3,552,000