Pension plans - Additional Information (Details) (Foreign Pension Plan, Defined Benefit, USD $) In Millions, unless otherwise specified	3 Months Ended
May 02, 2015
Foreign Pension Plan, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0.8
Estimated future employer contributions in next fiscal year	$ 2.4

Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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