Financial Instruments Reconciliation of the Change in Level 3 Items (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jul. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 32.4
Purchases	4.4
Settlements	(4.0)
Net unrealizrd gains (losses) included in earnings	(1.5)
Ending Balance	31.1
Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	10.7
Purchases	1.3
Settlements	0
Net unrealizrd gains (losses) included in earnings	(2.3)
Ending Balance	9.7
Convertible Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	17.5
Purchases	3.1
Settlements	0
Net unrealizrd gains (losses) included in earnings	0
Net unrealized gains (losses) included in other comprehensive income	0.8
Ending Balance	21.4
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	4.2
Purchases	0
Settlements	(4.0)
Net unrealizrd gains (losses) included in earnings	(0.2)
Ending Balance	$ 0