Employee Benefits - Pension Plans with Benefit Obligations in Excess of Plan Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Pension Plans with Projected Benefit Obligations in Excess of Plan Assets
Projected benefit obligation	$ 676	$ 6,829
Fair value of plan assets		5,838
Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets
Accumulated benefit obligation	$ 628	$ 553

Amount of plan asset for defined benefit pension plan with projected benefit obligation in excess of plan assets.

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- Definition

Amount of projected benefit obligation for defined benefit pension plan with projected benefit obligation in excess of plan assets.

+ References

+ Details

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- References

No definition available.

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- Definition

Amount of accumulated benefit obligation for defined benefit plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2417-114920

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2417-114920

+ Details

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- References

No definition available.

+ Details

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