Debt and Financing Activities - Revolving Credit Facilities and Lines of Credit (Details) € in Millions	1 Months Ended	6 Months Ended		12 Months Ended
	Oct. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Mar. 31, 2015 USD ($)	Oct. 29, 2015 USD ($)	Sep. 30, 2015 EUR (€)	Sep. 30, 2015 USD ($)
Revolving Credit Facility
Line of Credit Facility [Line Items]
Syndicated senior unsecured revolving credit facility							$ 1,300,000,000
Debt Instrument, Term		5 years
Syndicated unsecured revolving credit facility expiration date		Sep. 23, 2016
Interest rate description		bear interest based upon either the London Interbank Offered Rate or a prime rate
Borrowings under the facility		$ 0	$ 0
Amounts outstanding under facility				$ 0			0
Revolving Credit Facility | Celesio
Line of Credit Facility [Line Items]
Syndicated senior unsecured revolving credit facility							1,300,000,000
Borrowings under the facility		618,000,000	207,000,000
Amounts outstanding under facility				29,000,000			31,000,000
Repayments amount under credit lines		$ 616,000,000	33,000,000
Revolving Credit Facility | Celesio | Revolving Credit Facility Due February 2018
Line of Credit Facility [Line Items]
Syndicated senior unsecured revolving credit facility | €						€ 500
Syndicated unsecured revolving credit facility expiration date		Feb. 28, 2018
Borrowings under the facility		$ 0	0
Amounts outstanding under facility				0			0
New Credit Facility | Subsequent Event
Line of Credit Facility [Line Items]
Syndicated senior unsecured revolving credit facility					$ 3,500,000,000
Credit facility, aggregate sublimit	$ 3,150,000,000
Debt to capital covenant ratio					0.65
Accounts Receivable Sales Facility
Line of Credit Facility [Line Items]
Syndicated senior unsecured revolving credit facility							1,350,000,000
Borrowings under the facility		$ 0
Amounts outstanding under facility				$ 0			$ 0
Covenant compliance				we were in compliance with all covenants
Repayments amount under credit lines			$ 0