Disclosures About Derivative Instruments and Hedging Activities (Details 1) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Mar. 31, 2011
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Assets	$ 14.1	$ 28.0
Total Derivatives Liability	(136.5)	(24.6)
Designated as Hedging Instrument [Member]
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Assets	7.5	25.6
Total Derivatives Liability	(118.6)	(13.9)
Derivative Financial Instruments and Other Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Contracts [Member]
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Assets	4.4	12.3
Derivative Financial Instruments and Other Assets [Member] | Designated as Hedging Instrument [Member] | Foreign Currency Contracts [Member]
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Assets	3.1	0.3
Derivative Financial Instruments and Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Contracts [Member]
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Liability	(65.4)	(9.7)
Derivative Financial Instruments and Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Foreign Currency Contracts [Member]
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Liability		(4.0)
Derivative Financial Instruments and Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Liability	(53.2)	(0.2)
Derivative Financial Instruments and Other Noncurrent Liabilities [Member] | Accounted for Under ASC 980 [Member] | Commodity Contracts [Member]
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Liability	(17.9)	(10.7)
Derivative Financial Instruments [Member] | Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Assets		13.0
Derivative Financial Instruments [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Commodity Contracts [Member]
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Assets	6.6	0.8
Derivative Financial Instruments [Member] | Accounted for Under ASC 980 [Member] | Commodity Contracts [Member]
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Assets		$ 1.6