SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - 10K (Details)	12 Months Ended
Jan. 31, 2017 USD ($) T	Jan. 31, 2016 USD ($)
Cash and Cash Equivalents
Amount held by the Trust in a money market fund \| $	$ 13,695,168	$ 2,499,706
Revenue Recognition
Quantity of iron ore shipped by NMC subject to price determination recognized in revenue (in tons) \| T	1,055,909
Fixed Property, Including Intangibles
Percentage of fee interest owned by Mesabi Land Trust in the lands subject to the Peters Lease	20.00%

Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash Equivalents
-URI http://asc.fasb.org/extlink&oid=6507016

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant