Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 139		$ 270
Mortgage loan premium	4,026	[1]	5,888	[1]
Preferred shares of beneficial interest, liquidation preference value	$ 350,000		$ 325,000
Preferred shares of beneficial interest, par value	$ 0.01		$ 0.01
Preferred shares of beneficial interest, shares authorized	100,000,000		100,000,000
Preferred shares of beneficial interest, shares issued	14,000,000		13,000,000
Preferred shares of beneficial interest, shares outstanding	14,000,000		13,000,000
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	71,553,481		63,709,628
Common shares of beneficial interest, shares outstanding	71,553,481		63,709,628

[1] Loan premiums on assumed mortgages recorded in purchase accounting for the Hotel Palomar San Francisco, Embassy Suites San Diego Bay - Downtown, Hotel Modera and The Nines, a Luxury Collection Hotel, Portland.