Pensions and Post-Employment Benefits - Sensitivity Analysis of Pension and Other Post-Employment Benefits (Detail) $ in Millions	Dec. 31, 2020 USD ($)
Actuarial assumption of discount rates [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity, possible increase in actuarial assumption	$ (207)
Sensitivity, possible decrease in actuarial assumption	234
Actuarial assumption of expected rates of salary increases [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity, possible increase in actuarial assumption	8
Sensitivity, possible decrease in actuarial assumption	(7)
Actuarial assumption of expected rates of pension increases [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity, possible increase in actuarial assumption	146
Sensitivity, possible decrease in actuarial assumption	(128)
Pension defined benefit plans [member] \| Actuarial assumption of discount rates [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity, possible increase in actuarial assumption	(202)
Sensitivity, possible decrease in actuarial assumption	228
Pension defined benefit plans [member] \| Actuarial assumption of expected rates of salary increases [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity, possible increase in actuarial assumption	7
Sensitivity, possible decrease in actuarial assumption	(7)
Pension defined benefit plans [member] \| Actuarial assumption of expected rates of pension increases [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity, possible increase in actuarial assumption	146
Sensitivity, possible decrease in actuarial assumption	(128)
Other post employment benefits [Member] \| Actuarial assumption of discount rates [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity, possible increase in actuarial assumption	(5)
Sensitivity, possible decrease in actuarial assumption	6
Other post employment benefits [Member] \| Actuarial assumption of expected rates of salary increases [member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Sensitivity, possible increase in actuarial assumption	$ 1

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

No definition available.

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- Definition

The increase (decrease) in a defined benefit obligation that would have been caused by a decrease in a significant actuarial assumption that was reasonably possible at the end of the reporting period. [Refer: Actuarial assumptions [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2020-01-01
-Paragraph 145
-Subparagraph a
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- Definition

The increase (decrease) in a defined benefit obligation that would have been caused by an increase in a significant actuarial assumption that was reasonably possible at the end of the reporting period. [Refer: Actuarial assumptions [member]]

+ References

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