Reconciliation of the Change in Level 3 Items (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 28.7	$ 4.2
Purchases	9.0	24.5
Redemptions	(8.5)
Total realized/unrealized gains (losses) included in earnings	3.2
Ending Balance	32.4	28.7
Derivative
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	6.2	0
Purchases	2.0	6.2
Redemptions	(1.3)
Total realized/unrealized gains (losses) included in earnings	3.8
Ending Balance	10.7	6.2
Convertible Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	18.3
Purchases	7.0	18.3
Redemptions	(7.2)
Total realized/unrealized gains (losses) included in earnings	(0.6)
Ending Balance	17.5	18.3
Taxable auction rate securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	4.2	4.2
Purchases	0	0
Redemptions	0
Total realized/unrealized gains (losses) included in earnings	0
Ending Balance	$ 4.2	$ 4.2