Term Receivables and Trade Accounts Receivable - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jul. 31, 2012	Jul. 31, 2012	Jul. 31, 2011
Disclosure Term Receivables And Trade Accounts Receivable Additional Information [Abstract]
Billing Period	30 days
Net proceeds from sale of receivables		$ 8,452	$ 12,348

The cash inflow associated with the sale of receivables arising from the financing of goods and services.

No definition available.

Name:	us-gaap_ProceedsFromSaleOfFinanceReceivables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration