Benefit Plans - Fair Value Measurements of Plan Assets (Detail) - Pension Plans - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2,242	$ 3,222	$ 3,045
United States
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,537	2,189
United States | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	492	679
United States | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69	184
United States | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22	46
United States | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52	141
United States | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	469	686
United States | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	243	168
United States | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	191	286
Foreign Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	705	1,033
Foreign Plans | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33	55
Foreign Plans | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	13
Foreign Plans | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	180	264
Foreign Plans | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	76	121
Foreign Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	190	297
Foreign Plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	14
Foreign Plans | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	76	107
Foreign Plans | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35	44
Foreign Plans | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	96	118
Net Asset Value | United States
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	172	195
Net Asset Value | United States | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value | United States | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value | United States | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value | United States | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value | United States | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	62	43
Net Asset Value | United States | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value | United States | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	110	152
Level 1 | United States
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,068	1,405
Level 1 | United States | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	258	297
Level 1 | United States | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	53	162
Level 1 | United States | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 | United States | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26	0
Level 1 | United States | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	406	643
Level 1 | United States | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	243	168
Level 1 | United States | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	81	135
Level 1 | Foreign Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	508	765
Level 1 | Foreign Plans | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19	37
Level 1 | Foreign Plans | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8	10
Level 1 | Foreign Plans | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	167	249
Level 1 | Foreign Plans | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	68	72
Level 1 | Foreign Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	190	297
Level 1 | Foreign Plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	14
Level 1 | Foreign Plans | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48	84
Level 1 | Foreign Plans | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	2
Level 1 | Foreign Plans | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | United States
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	297	590
Level 2 | United States | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	234	382
Level 2 | United States | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	22
Level 2 | United States | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22	46
Level 2 | United States | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26	141
Level 2 | United States | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | United States | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | United States | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Foreign Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	68	124
Level 2 | Foreign Plans | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	18
Level 2 | Foreign Plans | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	3
Level 2 | Foreign Plans | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	15
Level 2 | Foreign Plans | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8	49
Level 2 | Foreign Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Foreign Plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Foreign Plans | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	8
Level 2 | Foreign Plans | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24	31
Level 2 | Foreign Plans | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | United States
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | United States | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | United States | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | United States | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | United States | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | United States | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | United States | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | United States | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Foreign Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	128	145
Level 3 | Foreign Plans | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Foreign Plans | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Foreign Plans | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Foreign Plans | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Foreign Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Foreign Plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Foreign Plans | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21	15
Level 3 | Foreign Plans | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	11
Level 3 | Foreign Plans | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 96	$ 118