Retention Retention receivable (Details) (USD $) In Millions, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Retention receivable [Line Items]
Retention receivable	$ 1.6	$ 0.6

Amount billed to customers under long-term contracts or programs that have been withheld because of retainage provisions in a contract to be collected in the next fiscal year following the latest fiscal year.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3

-Subparagraph c

-Article 5

Name:	us-gaap_ContractReceivableRetainageDueOneYearOrLess
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant