Commitments and Contingencies - Litigation (Details) SFr in Millions, $ in Millions	12 Months Ended
	Jan. 31, 2018 EUR (€)	Jan. 31, 2014 USD ($)	Jan. 31, 2014 CHF (SFr)	Jul. 31, 2018 USD ($)	Jul. 31, 2018 CHF (SFr)
Loss Contingencies [Line Items]
Loss contingency, damages paid, value | SFr			SFr 402.7
Arbitration award expense | $		$ 480.2
Litigation settlement, amount awarded to other party | €	€ 6,340
Swatch Parties [Member]
Loss Contingencies [Line Items]
Minimum damage claim sought by third party				$ 74.0	SFr 73.0
Maximum damage claim sought by third party				3,800.0	3,800.0
Tiffany Parties [Member]
Loss Contingencies [Line Items]
Minimum damage claim sought				121.0	120.0
Maximum damage claim sought				$ 547.0	SFr 540.0