Subsequent Events - Additional Information (Detail) - Graham [Member]		12 Months Ended
	Feb. 01, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Management fee, monthly basis		0.1458%
Management fee, annual basis		1.75%
Subsequent Event [Member]
Subsequent Event [Line Items]
Management fee, monthly basis	0.1125%
Management fee, annual basis	18.00%