Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified			9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011 6.75% Series D Preferred Shares [Member]	Dec. 31, 2010 6.75% Series D Preferred Shares [Member]	Sep. 30, 2011 6.95% Series E Preferred Shares [Member]	Dec. 31, 2010 6.95% Series E Preferred Shares [Member]	Sep. 30, 2011 6.5% Series F Preferred Shares [Member]	Dec. 31, 2010 6.5% Series F Preferred Shares [Member]
ASSETS
Allowance for doubtful accounts	$ 10,297	$ 10,137
Preferred Shares of Beneficial Interest - par value, $.03 per share; shares authorized: 10,000
Preferred Shares of Beneficial Interest; par value	$ 0.03	$ 0.03
Preferred Shares of Beneficial Interest; shares authorized	10,000	10,000
Preferred shares of beneficial interest; shares issued			100	100	29	29	140	140
Preferred shares of beneficial interest; shares outstanding			100	100	29	29	140	140
Preferred shares of beneficial interest; liquidation preference			$ 75,000	$ 75,000	$ 72,500	$ 72,500	$ 350,000	$ 350,000
Preferred stock, Dividend percentage			6.75%	6.75%	6.95%	6.95%	6.50%	6.50%
Common Shares of Beneficial Interest - par value	$ 0.03	$ 0.03
Common Shares of Beneficial Interest - shares authorized	275,000	275,000
Common Shares of Beneficial Interest - shares issued	120,840	120,492
Common Shares of Beneficial Interest - shares outstanding	120,840	120,492