Debt - Commercial Paper (Details) - USD ($) $ in Millions	3 Months Ended
	Oct. 31, 2017	Jan. 31, 2017	Oct. 31, 2016
Short-term Debt [Line Items]
Commercial Paper & Credit Facilities borrowing capacity	$ 750.0
Short-term borrowings	193.2	$ 228.7	$ 219.5
Commercial Paper [Member]
Short-term Debt [Line Items]
Commercial Paper, Maximum Borrowing Capacity	750.0
Short-term borrowings	$ 43.0
Short-term Debt, Weighted Average Interest Rate	1.28%
Four-year Credit Facility maturing October 2019 [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 375.0
Five-year Credit Facility maturing October 2020 [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 375.0