Beneficial Interest - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Beneficial Interest
Common shares, outstanding	9,547,000		9,436,000
Preferred shares, outstanding	0		0
Dividends paid	$ 0.2647	$ 0.2613
Dividends declared	$ 7,358	$ 7,035
Total Beneficial Interest
Beneficial Interest
Common shares, authorized	100,000,000
Common shares, par value	$ 0.01
Preferred shares, authorized	50,000,000
Preferred shares, par value	$ 0.01
Dividends declared	$ 2,527	$ 2,374