Financial Instruments Reconciliation of the Change in Level 3 Items (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jul. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 29.3
Purchases	0
Settlements	(4.4)
Net realized (losses)	(5.2)
Net unrealized (losses)	(1.4)
Ending Balance	18.3
Derivative Contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	9.1
Purchases	0
Settlements	(1.1)
Net realized (losses)	(3.0)
Net unrealized (losses)	(0.9)
Ending Balance	4.1
Convertible Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	20.2
Purchases	0
Settlements	(3.3)
Net realized (losses)	(2.2)
Net unrealized (losses)	(0.5)
Ending Balance	$ 14.2