Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Millions		Mar. 31, 2021	Sep. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		$ 162	$ 87
Derivative liabilities		3,012	3,020
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		538	441
Total liabilities		10	10
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		376	354
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		162	87
Total liabilities		10	10
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
Other Current Assets | Fair Value, Recurring [Member] | Exchange Traded Funds in Fixed Income securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]		19
Other Current Assets | Fair Value, Recurring [Member] | Exchange Traded Funds in Fixed Income securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]		0
Other Current Assets | Fair Value, Recurring [Member] | Exchange Traded Funds in Fixed Income securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]		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		77	27
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		77	27
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		3	2
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	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		3	2
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	0
Other Noncurrent Assets | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred Compensation Plan Assets		72	63
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred Compensation Plan Assets		72	63
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred Compensation Plan Assets		0	0
Other Noncurrent Assets | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred Compensation Plan Assets		0	0
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]	147	143
Other Noncurrent Assets | Fair Value, Recurring [Member] | Exchange Traded Funds in Fixed Income securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	147	143
Other Noncurrent Assets | Fair Value, Recurring [Member] | Exchange Traded Funds in Fixed Income securities [Member] | Fair Value, Inputs, Level 2 [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] | Exchange Traded Funds in Fixed Income securities [Member] | Fair Value, Inputs, Level 3 [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] | 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]	157	129
Other Noncurrent Assets | Fair Value, Recurring [Member] | Exchange traded funds in equity securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	157	129
Other Noncurrent Assets | Fair Value, Recurring [Member] | Exchange traded funds in equity securities [Member] | Fair Value, Inputs, Level 2 [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] | Exchange traded funds in equity securities [Member] | Fair Value, Inputs, Level 3 [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		82	58
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		82	58
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 | Fair Value, Recurring [Member] | Foreign Currency Exchange Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		10	10
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		10	10
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 22, "Commitments and Contingencies," of the notes to consolidated financial statements for further details.