Credit Risk Assessment for Long-term Receivables (Detail) - USD ($) $ in Thousands	Apr. 30, 2016	Jan. 31, 2016
Accounts and Financing Receivable [Line Items]
Term receivables, long-term	$ 253,636	$ 268,657
S&P credit rating, AAA+ through BBB-
Accounts and Financing Receivable [Line Items]
Term receivables, long-term	131,959	195,764
S&P credit rating, BB+ and lower
Accounts and Financing Receivable [Line Items]
Term receivables, long-term	80,904	22,520
S&P credit rating
Accounts and Financing Receivable [Line Items]
Term receivables, long-term	212,863	218,284
Internal Credit Rating
Accounts and Financing Receivable [Line Items]
Term receivables, long-term	$ 40,773	$ 50,373