Subsequent Events - Additional Information (Detail) - USD ($)		3 Months Ended
	Nov. 06, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Subsequent Event [Line Items]
Distribution per common unit (in dollars per share)		$ 0.08	$ 0.12	$ 0.23	$ 0	$ 0	$ 0	$ 0.06
Total cash distribution		$ 6,960,000	$ 10,440,000	$ 20,009,000	$ 0	$ 0	$ 0	$ 5,220,000
Subsequent Event
Subsequent Event [Line Items]
Distribution per common unit (in dollars per share)	$ 0.08
Total cash distribution	$ 6,960,000