Trading Advisors - Additional Information (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017
EMC [Member]
Schedule Of Trading Advisors [Line Items]
Management fee, monthly basis		0.0833%
Management fee, annual basis		1.00%
Incentive fee, monthly trading profits basis			20.00%
Graham [Member]
Schedule Of Trading Advisors [Line Items]
Management fee, monthly basis		0.1458%
Management fee, annual basis		1.75%
Incentive fee, monthly trading profits basis			20.00%
Rabar [Member]
Schedule Of Trading Advisors [Line Items]
Management fee, monthly basis			0.1667%
Management fee, annual basis			2.00%
Incentive fee, monthly trading profits basis			20.00%
Altis [Member]
Schedule Of Trading Advisors [Line Items]
Management fee, monthly basis	0.1042%
Management fee, annual basis	1.25%
Incentive fee, monthly trading profits basis	20.00%