Derivative Instruments and Hedging Activities - Effects of Derivative Instruments on the Condensed Consolidated Statements of Income and Changes in AOCI and Noncontrolling Interest (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Derivative Instruments, Gain (Loss)
Document Period End Date			Mar. 31, 2015
Derivatives Not Designated as Hedging Instruments
Derivative Instruments, Gain (Loss)
Gain (Loss) recognized in income	$ (16.9)	$ (22.2)	$ (306.1)	$ (9.3)
Cash Flow Hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in AOCI and Noncontrolling Interests	30.7	5.9	42.3	53.9
Gain (loss) reclassified from AOCI and Noncontrolling Interest into income	3.0	34.7	(0.6)	50.5
Commodity Contracts | Derivatives Not Designated as Hedging Instruments | Cost of Sales
Derivative Instruments, Gain (Loss)
Gain (Loss) recognized in income	(12.3)	(22.2)	(304.8)	(9.4)
Commodity Contracts | Derivatives Not Designated as Hedging Instruments | Revenues
Derivative Instruments, Gain (Loss)
Gain (Loss) recognized in income	(4.6)	0	(0.8)	0
Commodity Contracts | Derivatives Not Designated as Hedging Instruments | Operating Expenses / Other Operating Income, Net
Derivative Instruments, Gain (Loss)
Gain (Loss) recognized in income	0	0	(0.5)	0.1
Commodity Contracts | Cash Flow Hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in AOCI and Noncontrolling Interests	0	7.8	0	61.2
Commodity Contracts | Cash Flow Hedges | Cost of Sales
Derivative Instruments, Gain (Loss)
Gain (loss) reclassified from AOCI and Noncontrolling Interest into income	0.1	39.9	(2.3)	62.2
Foreign Currency Contracts | Cash Flow Hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in AOCI and Noncontrolling Interests	23.7	(0.2)	32.4	(2.7)
Foreign Currency Contracts | Cash Flow Hedges | Cost of Sales
Derivative Instruments, Gain (Loss)
Gain (loss) reclassified from AOCI and Noncontrolling Interest into income	6.5	(1.4)	9.2	(3.5)
Cross Currency Contracts | Cash Flow Hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in AOCI and Noncontrolling Interests	5.4	0.1	7.5	(1.1)
Cross Currency Contracts | Cash Flow Hedges | Interest Expense
Derivative Instruments, Gain (Loss)
Gain (loss) reclassified from AOCI and Noncontrolling Interest into income	(0.1)	0.2	(0.1)	(0.1)
Interest Rate Contracts | Cash Flow Hedges
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in AOCI and Noncontrolling Interests	1.6	(1.8)	2.4	(3.5)
Interest Rate Contracts | Cash Flow Hedges | Interest Expense / Other Operating Income, Net
Derivative Instruments, Gain (Loss)
Gain (loss) reclassified from AOCI and Noncontrolling Interest into income	$ (3.5)	$ (4.0)	$ (7.4)	$ (8.1)