Income Taxes U.S. Tax Reform (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Jan. 31, 2019	Oct. 31, 2018	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Statutory Accounting Practices [Line Items]
US Tax Act Impact					$ 95.4
US Tax Act Impact - Transition Tax	$ (25.2)	$ (24.0)		$ (49.2)	101.1
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability					$ (5.7)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%	21.00%	33.80%