Credit Risk Assessment for Long-term Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2013	Jan. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term receivables, long-term	$ 216,066	$ 250,497
S&P credit rating, AAA+ through BBB-
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term receivables, long-term	112,493	133,773
S&P credit rating, BB+ and lower
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term receivables, long-term	38,647	45,298
S&P credit rating
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term receivables, long-term	151,140	179,071
Internal Credit Rating
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term receivables, long-term	$ 64,926	$ 71,426