Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts	$ 71	$ 13
Preferred shares of beneficial interest, par value	$ 0.01	$ 0.01
Preferred shares of beneficial interest, liquidation preference value	$ 225,000	$ 0
Preferred shares of beneficial interest, shares authorized	100,000,000	100,000,000
Preferred shares of beneficial interest, shares issued	9,000,000	0
Preferred shares of beneficial interest, shares outstanding	9,000,000	0
Common shares of beneficial interest, par value	$ 0.01	$ 0.01
Common shares of beneficial interest, shares authorized	500,000,000	500,000,000
Common shares of beneficial interest, shares issued	50,769,024	39,814,760
Common shares of beneficial interest, shares outstanding	50,769,024	39,814,760