Financial Instruments Reconciliation of the Change in Level 3 Items (Details) - Level 3 $ in Millions	6 Months Ended
	Jul. 31, 2016 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 31, 2016	$ 3.7
Purchases	4.9
Losses included in earnings	(0.2)
Gains included in OCI	0.2
Balance at July 31, 2016	8.6
Derivative Contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 31, 2016	0.3
Purchases	0.9
Losses included in earnings	0.0
Gains included in OCI	0.0
Balance at July 31, 2016	1.2
Convertible Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 31, 2016	3.4
Purchases	4.0
Losses included in earnings	(0.2)
Gains included in OCI	0.2
Balance at July 31, 2016	$ 7.4