ROYALTY AGREEMENT, UNALLOCATED RESERVE AND DISTRIBUTIONS (Details) - USD ($)		3 Months Ended		9 Months Ended
	Oct. 11, 2019	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018	Jan. 31, 2019
UNALLOCATED RESERVE AND DISTRIBUTIONS
Distribution declared per unit (Note 3) (in dollars per unit)		$ 0.8700	$ 0.9400	$ 1.9700	$ 1.6100
Unallocated Cash and Securities portion of Unallocated Reserve
Cash and U.S. Government securities		$ 25,936,560		$ 25,936,560		$ 33,004,122
Distribution payable		(11,414,408)		(11,414,408)		(18,236,814)
Unallocated cash and U.S. Government securities		14,522,152		14,522,152		$ 14,767,308
Reconciliation of Trust's Unallocated Reserve
Beginning Balance		21,195,656	$ 27,003,575	16,805,692	$ 10,606,678
Net income		6,150,196	13,585,062	24,972,171	38,772,365
Distributions declared		(11,414,408)	(12,332,810)	(25,846,419)	(21,123,216)
Ending Balance		15,931,444	28,255,827	15,931,444	28,255,827
Distribution declared per unit	$ 0.87
Unallocated Reserve
Reconciliation of Trust's Unallocated Reserve
Beginning Balance		21,195,653	27,003,572	16,805,689	10,606,675
Net income		6,150,196	13,585,062	24,972,171	38,772,365
Distributions declared		(11,414,408)	(12,332,810)	(25,846,419)	(21,123,216)
Ending Balance		15,931,441	28,255,824	15,931,441	28,255,824
Trust Corpus
Reconciliation of Trust's Unallocated Reserve
Beginning Balance		3	3	3	3
Ending Balance		$ 3	$ 3	$ 3	$ 3