Fair Value on a Recurring Basis (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Mar. 31, 2011
Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents	$ 844.6		$ 1,100.2
Short-term marketable securities	13.8		14.1
Long-term investments	1.4		1.4
Fair Value of Total Assets, Recurring	859.8		1,115.7
Fair value of assets measured on a recurring basis, percentage of total assets	7.30%		9.20%
Interest rate swap agreements	0	[1]	0	[1]
Mandatorily redeemable noncontrolling interests	0	[2]	0	[2]
Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents	0		0
Short-term marketable securities	0		0
Long-term investments	9.2		13.9
Fair Value of Total Assets, Recurring	9.2		13.9
Fair value of assets measured on a recurring basis, percentage of total assets	0.10%		0.10%
Interest rate swap agreements	2.8	[1]	0.3	[1]
Mandatorily redeemable noncontrolling interests	0	[2]	0	[2]
Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents	0		0
Short-term marketable securities	0		0
Long-term investments	0		0
Fair Value of Total Assets, Recurring	0		0
Fair value of assets measured on a recurring basis, percentage of total assets	0.00%		0.00%
Interest rate swap agreements	0	[1]	0	[1]
Mandatorily redeemable noncontrolling interests	25.8	[2]	57.9	[2]
Fair Value, Total
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents	844.6		1,100.2
Short-term marketable securities	13.8		14.1
Long-term investments	10.6		15.3
Fair Value of Total Assets, Recurring	869.0		1,129.6
Fair value of assets measured on a recurring basis, percentage of total assets	7.40%		9.30%
Interest rate swap agreements	2.8	[1]	0.3	[1]
Mandatorily redeemable noncontrolling interests	$ 25.8	[2]	$ 57.9	[2]

[1] Our interest rate swap agreements are cash flow or fair value hedges whose fair value was derived from the present value of future cash flows using valuation models that were based on readily observable market data such as interest rates and yield curves.

[2] Relates to unconditional obligations to purchase additional noncontrolling equity shares of consolidated subsidiaries. Fair value measurement of the obligation was based upon the amount payable as if the forward contracts were settled. The amount redeemable within the next twelve months is classified in accrued liabilities; any interests redeemable thereafter are classified in other non-current liabilities.