Financial Instruments and Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Remaining cash equivalents	$ 12,153,000,000	$ 1,317,000,000
Fair value of long-term debt	19,200,000,000	11,300,000,000
Fair value of debt classified from long term to short term	206,000,000	798,000,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	40,000,000
Transfer of assets in and out of level 1, 2 and 3 measurements during the period	0	0
Transfer of liabilities in and out of level 1, 2 and 3 measurements during the period	$ 0	0
Capitalized Computer Software, Impairments		214,000,000
Asset Impairment Charges			$ 72,000,000
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity period of short-term investments at the time of purchase	3 months
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity period of short-term investments at the time of purchase	1 year
Respiratory Solutions | Disposal Group, Held-for-sale, Not Discontinued Operations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (Loss) on Disposition of Business		$ (81,000,000)