CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Sep. 30, 2011	Dec. 31, 2010
CONDENSED CONSOLIDATED BALANCE SHEETS
Common shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares of beneficial interest, shares authorized	174,700,000	174,700,000
Common shares of beneficial interest, shares issued	153,446,046	141,854,657
Common shares of beneficial interest, shares outstanding	153,446,046	141,854,657