Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Millions		Jun. 30, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		$ 70	$ 97
Derivative liabilities		2,627	2,568
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		412	441
Total liabilities		25	24
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		342	344
Total liabilities		0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		70	97
Total liabilities		25	24
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		0	0
Total liabilities		0	0
Other Current Assets | Fair Value, Recurring [Member] | Exchange Traded Funds in Fixed Income securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	19	19
Other Current Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange Traded Funds in Fixed Income securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	19	19
Other Current Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange Traded Funds in Fixed Income securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	0	0
Other Current Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange Traded Funds in Fixed Income securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	0	0
Other Current Assets | Fair Value, Recurring [Member] | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		20	35
Other Current Assets | Fair Value, Recurring [Member] | Foreign Currency Exchange Derivatives | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Other Current Assets | Fair Value, Recurring [Member] | Foreign Currency Exchange Derivatives | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		20	35
Other Current Assets | Fair Value, Recurring [Member] | Foreign Currency Exchange Derivatives | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Other Current Assets | Fair Value, Recurring [Member] | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		1
Other Current Assets | Fair Value, Recurring [Member] | Commodity Derivatives | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0
Other Current Assets | Fair Value, Recurring [Member] | Commodity Derivatives | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		1
Other Current Assets | Fair Value, Recurring [Member] | Commodity Derivatives | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0
Other Noncurrent Assets | Fair Value, Recurring [Member] | Deferred compensation plan assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure		61	71
Other Noncurrent Assets | Fair Value, Recurring [Member] | Exchange Traded Funds in Fixed Income securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	142	138
Other Noncurrent Assets | Fair Value, Recurring [Member] | Exchange traded funds in equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	120	116
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Deferred compensation plan assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure		61	71
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange Traded Funds in Fixed Income securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	142	138
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange traded funds in equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	120	116
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Deferred compensation plan assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure		0	0
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange Traded Funds in Fixed Income securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	0	0
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange traded funds in equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	0	0
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Deferred compensation plan assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure		0	0
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange Traded Funds in Fixed Income securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	0	0
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange traded funds in equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	0	0
Other Noncurrent Assets | Fair Value, Recurring [Member] | Equity swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		49	62
Other Noncurrent Assets | Fair Value, Recurring [Member] | Equity swap | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Other Noncurrent Assets | Fair Value, Recurring [Member] | Equity swap | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		49	62
Other Noncurrent Assets | Fair Value, Recurring [Member] | Equity swap | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Other Current Liabilities | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities			1
Other Current Liabilities | Commodity Derivatives | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities			0
Other Current Liabilities | Commodity Derivatives | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities			1
Other Current Liabilities | Commodity Derivatives | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities			0
Other Current Liabilities | Fair Value, Recurring [Member] | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		25	23
Other Current Liabilities | Fair Value, Recurring [Member] | Foreign Currency Exchange Derivatives | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		0	0
Other Current Liabilities | Fair Value, Recurring [Member] | Foreign Currency Exchange Derivatives | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		25	23
Other Current Liabilities | Fair Value, Recurring [Member] | Foreign Currency Exchange Derivatives | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		$ 0	$ 0

[1] ¹ Classified as restricted investments for payment of asbestos liabilities. See Note 21, "Commitments and Contingencies," of the notes to consolidated financial statements for further details.