Credit Risk Assessment for Long-term Receivables (Detail) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Accounts and Financing Receivable [Line Items]
Term receivables, long-term	$ 226,268	$ 268,657
S&P credit rating, AAA+ through BBB-
Accounts and Financing Receivable [Line Items]
Term receivables, long-term	164,331	195,764
S&P credit rating, BB+ and lower
Accounts and Financing Receivable [Line Items]
Term receivables, long-term	32,900	22,520
S&P credit rating
Accounts and Financing Receivable [Line Items]
Term receivables, long-term	197,231	218,284
Internal Credit Rating
Accounts and Financing Receivable [Line Items]
Term receivables, long-term	$ 29,037	$ 50,373