Retention Retention receivable (Details) (USD $) In Millions, unless otherwise specified	Jan. 31, 2015	Jan. 31, 2014
Retention receivable [Line Items]
Retention receivable	$ 5.7	$ 5.0

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. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 910

-SubTopic 310

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6471494&loc=d3e49370-109356

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