Debt and Financing Arrangements (Details Textuals) (USD $) In Millions	12 Months Ended		3 Months Ended		12 Months Ended
	Sep. 30, 2011 Revolving credit facility [Member]	Sep. 30, 2010 Revolving credit facility [Member]	Mar. 31, 2011 Revolving credit facility [Member] Committed Five-year Credit Facility Expiring in December 2011 [Member]	Mar. 31, 2011 Revolving credit facility [Member] Committed Four-year Credit Facility Expiring in February 2015 [Member]	Sep. 30, 2011 Commercial Paper [Member]	Sep. 30, 2010 Commercial Paper [Member]
Debt and Financing Arrangements (Textuals)
Total credit facility available			$ 2,050.0	$ 2,500.0
Length of credit facility, years			5 years	4 years
Facility expiry date			December 2011	February 2015
Maximum amount drawn on the credit facilities during period	0	0
Average outstanding commercial paper					955	342
Outstanding commercial paper at period end					$ 409	$ 0