Derivative Instruments and Hedging Activities - Location and Fair Values of Derivative Instruments and Hedging Activities (Detail) € in Millions, shares in Millions, $ in Millions, ¥ in Billions	3 Months Ended		6 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($) T Swap shares	Dec. 31, 2016	Mar. 31, 2018 USD ($) T Swap	Sep. 30, 2017 USD ($) T Swap shares	Mar. 31, 2018 EUR (€) T Swap	Mar. 31, 2018 JPY (¥) T Swap	Sep. 30, 2017 EUR (€) T Swap	Sep. 30, 2017 JPY (¥) T Swap	Sep. 30, 2016 USD ($) Swap
Derivative Instruments [Line Items]
Hedge Percentage For Foreign Exchange Transactional Exposures Minimum			70.00%
Hedge Percentage For Foreign Exchange Transactional Exposures Maximum			90.00%
Number of Interest Rate Derivatives Held | Swap	0		0	0	0	0	0	0
Number of interest rate derivatives terminated		4
Derivative, amount of hedged ordinary shares | shares	1.8			1.4
Derivative assets	$ 92		$ 92	$ 91
Derivative liabilities	$ 3,120		$ 3,120	$ 2,105
Copper [Member]
Derivative Instruments [Line Items]
Derivative, Nonmonetary Notional Amount | T	3,901		3,901	1,962	3,901	3,901	1,962	1,962
Polypropylene [Member]
Derivative Instruments [Line Items]
Derivative, Nonmonetary Notional Amount | T	16,561		16,561	19,563	16,561	16,561	19,563	19,563
Lead [Member]
Derivative Instruments [Line Items]
Derivative, Nonmonetary Notional Amount | T	6,500		6,500	24,705	6,500	6,500	24,705	24,705
Aluminum [Member]
Derivative Instruments [Line Items]
Derivative, Nonmonetary Notional Amount | T	4,525		4,525	2,169	4,525	4,525	2,169	2,169
Tin [Member]
Derivative Instruments [Line Items]
Derivative, Nonmonetary Notional Amount | T	2,015		2,015	1,715	2,015	2,015	1,715	1,715
Equity swap
Derivative Instruments [Line Items]
Derivative, Amount of Hedged Item	$ 73		$ 73	$ 58
Foreign Currency Denominated Debt [Member]
Derivative Instruments [Line Items]
Notional amount | ¥						¥ 35		¥ 35
Designated as Hedging Instrument
Derivative Instruments [Line Items]
Derivative assets	29		29	36
Derivative liabilities	3,098		3,098	2,080
Designated as Hedging Instrument | Other Current Assets | Foreign Currency Exchange Derivatives
Derivative Instruments [Line Items]
Derivative assets	26		26	27
Designated as Hedging Instrument | Other Current Assets | Commodity Derivatives
Derivative Instruments [Line Items]
Derivative assets	3		3	9
Designated as Hedging Instrument | Other Noncurrent Assets | Equity swap
Derivative Instruments [Line Items]
Derivative assets	0		0	0
Designated as Hedging Instrument | Other Current Liabilities | Foreign Currency Exchange Derivatives
Derivative Instruments [Line Items]
Derivative liabilities	15		15	21
Designated as Hedging Instrument | Other Current Liabilities | Commodity Derivatives
Derivative Instruments [Line Items]
Derivative liabilities	2		2	1
Designated as Hedging Instrument | Long-term Debt | Foreign Currency Denominated Debt [Member]
Derivative Instruments [Line Items]
Derivative liabilities	3,081		3,081	2,058
Not Designated as Hedging Instrument
Derivative Instruments [Line Items]
Derivative assets	63		63	55
Derivative liabilities	22		22	25
Not Designated as Hedging Instrument | Other Current Assets | Foreign Currency Exchange Derivatives
Derivative Instruments [Line Items]
Derivative assets	0		0	0
Not Designated as Hedging Instrument | Other Current Assets | Commodity Derivatives
Derivative Instruments [Line Items]
Derivative assets	0		0	0
Not Designated as Hedging Instrument | Other Noncurrent Assets | Equity swap
Derivative Instruments [Line Items]
Derivative assets	63		63	55
Not Designated as Hedging Instrument | Other Current Liabilities | Foreign Currency Exchange Derivatives
Derivative Instruments [Line Items]
Derivative liabilities	22		22	25
Not Designated as Hedging Instrument | Other Current Liabilities | Commodity Derivatives
Derivative Instruments [Line Items]
Derivative liabilities	0		0	0
Not Designated as Hedging Instrument | Long-term Debt | Foreign Currency Denominated Debt [Member]
Derivative Instruments [Line Items]
Derivative liabilities	$ 0		$ 0	$ 0
One Point Four Percent Due Two Thousand Eighteen | Interest Rate Swaps
Derivative Instruments [Line Items]
Number of Interest Rate Derivatives Held | Swap									3
Notional amount									$ 300
Debt Instrument, Interest Rate, Stated Percentage									1.40%
2.6% due 2017 | Interest Rate Swaps
Derivative Instruments [Line Items]
Number of Interest Rate Derivatives Held | Swap									4
Notional amount									$ 400
Debt Instrument, Interest Rate, Stated Percentage									2.60%
7.125% due 2017 | Interest Rate Swaps
Derivative Instruments [Line Items]
Number of Interest Rate Derivatives Held | Swap									1
Notional amount									$ 150
Debt Instrument, Interest Rate, Stated Percentage									7.125%
One billion euro net investment hedge [Member] | Foreign Currency Denominated Debt [Member]
Derivative Instruments [Line Items]
Notional amount | €					€ 1,000		€ 1,000
423 million euro net investment hedge [Member] | Foreign Currency Denominated Debt [Member]
Derivative Instruments [Line Items]
Notional amount | €					423		423
58 million euro net investment hedge [Member] | Foreign Currency Denominated Debt [Member]
Derivative Instruments [Line Items]
Notional amount | €					€ 58		€ 58