Accumulated other comprehensive income (loss) - Changes in Accumulated OCI by Component and Reclassifications Out of Accumulated OCI (Details) $ in Millions	9 Months Ended
Oct. 31, 2020 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 1,222.6
Other comprehensive income (loss) (“OCI”) before reclassifications	(10.6)
Amounts reclassified from AOCI to net income	(10.0)
Net current period OCI	(20.6)
Ending Balance	915.9
Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(250.1)
Other comprehensive income (loss) (“OCI”) before reclassifications	(11.1)
Amounts reclassified from AOCI to net income	0.0
Net current period OCI	(11.1)
Ending Balance	(261.2)
Gains (losses) on available-for-sale securities, net
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	0.3
Other comprehensive income (loss) (“OCI”) before reclassifications	0.3
Amounts reclassified from AOCI to net income	0.0
Net current period OCI	0.3
Ending Balance	0.6
Gains (losses) on cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	12.5
Other comprehensive income (loss) (“OCI”) before reclassifications	0.2
Amounts reclassified from AOCI to net income	(10.8)
Net current period OCI	(10.6)
Ending Balance	1.9
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(293.8)
Ending Balance	(314.4)
Pension Plan \| Actuarial gains (losses)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(52.4)
Other comprehensive income (loss) (“OCI”) before reclassifications	0.0
Amounts reclassified from AOCI to net income	0.2
Net current period OCI	0.2
Ending Balance	(52.2)
Pension Plan \| Prior service credits (costs)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(4.1)
Other comprehensive income (loss) (“OCI”) before reclassifications	0.0
Amounts reclassified from AOCI to net income	0.6
Net current period OCI	0.6
Ending Balance	$ (3.5)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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