Contingencies (Details) £ in Millions, $ in Millions			3 Months Ended	26 Months Ended
	Jan. 19, 2018 GBP (£)	Dec. 20, 2017 GBP (£)	Jan. 31, 2018 GBP (£)	Apr. 30, 2017 action	Jul. 31, 2017 USD ($)
Operating Loss Carryforwards [Line Items]
Number of putative class action complaints filed (over) | action				50
Litigation Settlement, Amount | $					$ 3.0
UNITED KINGDOM
Operating Loss Carryforwards [Line Items]
Diverted profit tax		£ 31.0	£ 31.0
DPT payment	£ 31.0