UNALLOCATED RESERVE AND DISTRIBUTIONS (Details) (USD $)	3 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Jan. 31, 2013
UNALLOCATED RESERVE AND DISTRIBUTIONS
Cash and U.S. Government securities	$ 1,868,467		$ 7,373,331
Distribution payable	(1,049,601)		(6,428,805)
Unallocated cash and U.S. Government securities	818,866		944,526
Reconciliation of unallocated reserve
Unallocated reserve at the beginning of the period	1,182,222
Net income	2,202,389	3,369,892
Distributions declared	(1,049,601)
Unallocated reserve at the end of the period	2,335,010
Within a range of not less
UNALLOCATED RESERVE AND DISTRIBUTIONS
Unallocated cash and U.S. Government securities	500,000
Within a range of not more
UNALLOCATED RESERVE AND DISTRIBUTIONS
Unallocated cash and U.S. Government securities	$ 1,000,000