Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
ASSETS
Allowance for doubtful accounts	$ 10,199	$ 12,127
Preferred Shares of Beneficial Interest - par value, $.03 per share; shares authorized: 10,000
Preferred Shares of Beneficial Interest; par value per share	$ 0.03	$ 0.03
Preferred Shares of Beneficial Interest; shares authorized	10,000	10,000
Common Shares of Beneficial Interest - par value, $.03 per share; shares authorized: 275,000; shares issued and outstanding: 121,940 in 2013 and 121,505 in 2012
Common Shares of Beneficial Interest; par value per share	$ 0.03	$ 0.03
Common Shares of Beneficial Interest; shares authorized	275,000	275,000
Common Shares of Beneficial Interest; shares issued	121,940	121,505
Common Shares of Beneficial Interest; shares outstanding	121,940	121,505
6.75% Series D Preferred Shares [Member]
Preferred Shares of Beneficial Interest - par value, $.03 per share; shares authorized: 10,000
Preferred Shares of Beneficial Interest; shares issued	100	100
Preferred Shares of Beneficial Interest; shares outstanding	0	100
Preferred Shares of Beneficial Interest; liquidation preference	0	75,000
Preferred Shares of Beneficial Interest; dividend percentage	6.75%	6.75%
6.5% Series F Preferred Shares [Member]
Preferred Shares of Beneficial Interest - par value, $.03 per share; shares authorized: 10,000
Preferred Shares of Beneficial Interest; shares issued	140	140
Preferred Shares of Beneficial Interest; shares outstanding	60	140
Preferred Shares of Beneficial Interest; liquidation preference	$ 150,000	$ 350,000
Preferred Shares of Beneficial Interest; dividend percentage	6.50%	6.50%