Shareholders' Equity - Additional Information (Details) $ / shares in Units, $ in Thousands									3 Months Ended				9 Months Ended
	Oct. 15, 2020 USD ($) $ / shares	Sep. 21, 2020 $ / shares shares	Sep. 17, 2020 $ / shares shares	Aug. 20, 2020 USD ($)	Jun. 10, 2020 trustee $ / shares shares	May 21, 2020 USD ($)	Feb. 27, 2020 trustee $ / shares shares	Feb. 20, 2020 USD ($)	Jun. 30, 2020 $ / shares shares	Mar. 31, 2020 $ / shares shares	Sep. 30, 2019 shares	Jun. 30, 2019 shares	Sep. 30, 2020 USD ($)
Class of Stock [Line Items]
Common stock dividend | $				$ 1,646		$ 1,646		$ 88,863					$ 92,155
Number of new trustees | trustee					7		2
Shares repurchased (in shares) | shares		38,156							3,808	2,637
Shares repurchased (in dollars per share) | $ / shares		$ 7.40							$ 7.09	$ 16.36
Common Shares
Class of Stock [Line Items]
Shares granted (in shares) | shares			264,400
Shares granted valued (in dollars per share) | $ / shares			$ 8.44
Shares repurchased (in shares) | shares										2,637	29,334	2,172
Trustee One | Common Shares
Class of Stock [Line Items]
Shares granted (in shares) | shares					5,000		3,000
Shares granted valued (in dollars per share) | $ / shares					$ 10.80		$ 18.64
Trustee Two | Common Shares
Class of Stock [Line Items]
Shares granted (in shares) | shares					5,000		3,000
Shares granted valued (in dollars per share) | $ / shares					$ 10.80		$ 18.64
Trustee Three | Common Shares
Class of Stock [Line Items]
Shares granted (in shares) | shares					5,000
Shares granted valued (in dollars per share) | $ / shares					$ 10.80
Trustee Four | Common Shares
Class of Stock [Line Items]
Shares granted (in shares) | shares					5,000
Shares granted valued (in dollars per share) | $ / shares					$ 10.80
Trustee Five | Common Shares
Class of Stock [Line Items]
Shares granted (in shares) | shares					5,000
Shares granted valued (in dollars per share) | $ / shares					$ 10.80
Trustee Six | Common Shares
Class of Stock [Line Items]
Shares granted (in shares) | shares					5,000
Shares granted valued (in dollars per share) | $ / shares					$ 10.80
Trustee Seven | Common Shares
Class of Stock [Line Items]
Shares granted (in shares) | shares					5,000
Shares granted valued (in dollars per share) | $ / shares					$ 10.80
Subsequent event
Class of Stock [Line Items]
Quarterly distribution declared (in dollars per share) | $ / shares	$ 0.01
Common stock dividend | $	$ 1,646