Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 738	$ 526
Preferred shares of beneficial interest, liquidation preference value	$ 510,000	$ 510,000
Preferred shares of beneficial interest, par value (usd per share)	$ 0.01	$ 0.01
Preferred shares of beneficial interest, authorized (in shares)	100,000,000	100,000,000
Preferred shares of beneficial interest, issued (in shares)	20,400,000	20,400,000
Preferred shares of beneficial interest, outstanding (in shares)	20,400,000	20,400,000
Common shares of beneficial interest, par value (usd per share)	$ 0.01	$ 0.01
Common shares of beneficial interest, authorized (in shares)	500,000,000	500,000,000
Common shares of beneficial interest, issued (in shares)	130,484,956	130,311,289
Common shares of beneficial interest, outstanding (in shares)	130,484,956	130,311,289