CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Preferred shares of beneficial interest, shares issued (in shares)	4,915,196	4,915,196
Preferred shares, of beneficial interest, shares outstanding (in shares)	4,915,196	4,915,196
Preferred shares, aggregate liquidation preference	$ 122,880	$ 122,880
Common shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares of beneficial interest, shares authorized (in shares)	350,000,000	350,000,000
Common shares of beneficial interest, shares issued (in shares)	121,924,199	121,572,155
Common shares of beneficial interest, shares outstanding (in shares)	121,924,199	121,572,155
Series D Preferred Stock
Preferred shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred shares of beneficial interest, shares authorized (in shares)	50,000,000	50,000,000