Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Allowance for doubtful accounts	$ 7,680	$ 9,386
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
Common Shares of Beneficial Interest - par value, $.03 per share; shares authorized: 275,000; shares issued and outstanding: 122,489 in 2014 and 121,949 in 2013
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	122,489	121,949
Common shares of beneficial interest, shares outstanding	122,489	121,949
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	60
Preferred shares of beneficial interest, liquidation preference	$ 150,000	$ 150,000
Preferred shares of beneficial interest, dividend percentage	6.50%	6.50%