Accumulated other comprehensive income (loss) - Changes in Accumulated OCI by Component and Reclassifications Out of Accumulated OCI (Details) $ in Millions	6 Months Ended
	Jul. 29, 2017 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	$ 2,490.2
Other comprehensive income (“OCI”) before reclassifications	27.4
Amounts reclassified from AOCI to net income	(2.0)
Total other comprehensive (loss) income	25.4
Balance	2,176.6
Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(263.4)
Other comprehensive income (“OCI”) before reclassifications	25.1
Amounts reclassified from AOCI to net income	0.0
Total other comprehensive (loss) income	25.1
Balance	(238.3)
Losses on available-for-sale securities, net
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(0.4)
Other comprehensive income (“OCI”) before reclassifications	0.5
Amounts reclassified from AOCI to net income	0.0
Total other comprehensive (loss) income	0.5
Balance	0.1
Gains (losses) on cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	2.4
Other comprehensive income (“OCI”) before reclassifications	1.8
Amounts reclassified from AOCI to net income	(2.5)
Total other comprehensive (loss) income	(0.7)
Balance	1.7
Accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(307.7)
Balance	(282.3)
Pension Plan | Actuarial losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(55.5)
Other comprehensive income (“OCI”) before reclassifications	0.0
Amounts reclassified from AOCI to net income	1.2
Total other comprehensive (loss) income	1.2
Balance	(54.3)
Pension Plan | Prior service credits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	9.2
Other comprehensive income (“OCI”) before reclassifications	0.0
Amounts reclassified from AOCI to net income	(0.7)
Total other comprehensive (loss) income	(0.7)
Balance	$ 8.5