Restructuring and other exit costs, net (Narrative) (Details) - Scenario, Forecast - Fiscal 2018 Plan	12 Months Ended
Jan. 31, 2019 Position
Restructuring Cost and Reserve [Line Items]
Expected termination of workforce, percent	13.00%
Restructuring, number of positions eliminated	1,150

The number of positions eliminated during the period as a percentage of total positions eliminated during the period in connection with the restructuring plan(s).

No definition available.

Name:	us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminatedPeriodPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration