UNALLOCATED RESERVE AND DISTRIBUTIONS (Details) - USD ($)		3 Months Ended		9 Months Ended
	Oct. 09, 2020	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Jan. 31, 2020
Unallocated Cash and Securities portion of Unallocated Reserve
Cash and U.S. Government securities		$ 15,402,232		$ 15,402,232		$ 23,510,129
Distribution payable		(4,723,204)		(4,723,204)		(9,184,007)
Unallocated cash and U.S. Government securities		10,679,028		10,679,028		$ 14,326,122
Reconciliation of Trust's Unallocated Reserve
Beginning Balance		12,115,434	$ 21,195,656	11,831,017	$ 16,805,692
Net income		5,126,399	6,150,196	13,414,023	24,972,171
Distributions declared		(4,723,204)	(11,414,408)	(12,726,411)	(25,846,419)
Ending Balance		$ 12,518,629	$ 15,931,444	$ 12,518,629	$ 15,931,444
Distributions declared per unit (in dollars per unit)	$ 0.36	$ 0.3600	$ 0.8700	$ 0.9700	$ 1.9700
Unallocated Reserve
Reconciliation of Trust's Unallocated Reserve
Beginning Balance		$ 12,115,431	$ 21,195,653	$ 11,831,014	$ 16,805,689
Net income		5,126,399	6,150,196	13,414,023	24,972,171
Distributions declared		(4,723,204)	(11,414,408)	(12,726,411)	(25,846,419)
Ending Balance		12,518,626	15,931,441	12,518,626	15,931,441
Trust Corpus
Reconciliation of Trust's Unallocated Reserve
Beginning Balance		3	3	3	3
Ending Balance		$ 3	$ 3	$ 3	$ 3