Debt and Financing Activities - Accounts Receivable Facilities (Details) - USD ($)	6 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2015	Oct. 29, 2015
Accounts Receivable Sales Facility
Line of Credit Facility [Line Items]
Accounts receivable sales facility committed balance	$ 1,350,000,000
Borrowings under the facility	0
Borrowings and related securitized accounts receivable outstanding	0		$ 0
Covenant compliance			we were in compliance with all covenants
Repayments of short term borrowings under the facilities		$ 0
New Credit Facility | Subsequent Event
Line of Credit Facility [Line Items]
Accounts receivable sales facility committed balance				$ 3,500,000,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Accounts receivable sales facility committed balance	1,300,000,000
Borrowings under the facility	0	0
Borrowings and related securitized accounts receivable outstanding	$ 0		$ 0
Factoring facilities expiration	Sep. 23, 2016
Revolving Credit Facility | Celesio
Line of Credit Facility [Line Items]
Accounts receivable sales facility committed balance	$ 1,300,000,000
Borrowings under the facility	618,000,000	207,000,000
Borrowings and related securitized accounts receivable outstanding	31,000,000		29,000,000
Repayments of short term borrowings under the facilities	616,000,000	33,000,000
Accounts Receivable Factoring Facility | Celesio
Line of Credit Facility [Line Items]
Accounts receivable sales facility committed balance	172,000,000
Borrowings under the facility	883,000,000	1,575,000,000
Borrowings and related securitized accounts receivable outstanding	139,000,000		$ 135,000,000
Repayments of short term borrowings under the facilities	$ 887,000,000	$ 1,545,000,000
Factoring facilities expiration	Jan. 31, 2016