NATURE OF BUSINESS AND ORGANIZATION (Details)	6 Months Ended
Jul. 31, 2021 item
NATURE OF BUSINESS AND ORGANIZATION
Number of members on panel for arbitration	3

The number of members appointed to the panel for arbitration.

No definition available.

Name:	msb_ArbitrationNumberOfMembersOnPanel
Namespace Prefix:	msb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration