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Pension and Other Postretirement Benefit Plans - Fair Values of Pension Plan Assets (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 860	$ 826
United States
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,361	9,648	$ 10,896
United States | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	239	222
United States | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,747	3,190
United States | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	888	841
United States | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	173	161
United States | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	32
United States | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,451	2,172
United States | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,094	1,509
United States | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,582	1,246
United States | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	178	262
United States | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	13
United States | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,824	2,502
United States | Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	40
United States | Level 1 | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	205	169
United States | Level 1 | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	165	121
United States | Level 1 | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 1 | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 1 | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,451	2,172
United States | Level 1 | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 1 | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 1 | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 1 | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,854	3,017
United States | Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 2 | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 2 | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 2 | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 2 | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 2 | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 2 | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,094	1,509
United States | Level 2 | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,582	1,246
United States | Level 2 | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	178	262
United States | Level 2 | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	13	15
United States | Level 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 3 | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 3 | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 3 | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 3 | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 3 | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0	0
United States | Level 3 | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 3 | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 3 | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 3 | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Level 3 | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0	0
United States | Level 3 | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	13	15
United States | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,674	4,116
United States | NAV | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	236	182
United States | NAV | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,542	3,021
United States | NAV | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	723	720
United States | NAV | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	173	161
United States | NAV | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	32
United States | NAV | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | NAV | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | NAV | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | NAV | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | NAV | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10,163	8,580	9,339
International | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	86	69
International | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,403	3,607
International | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	252	251
International | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,203	2,634
International | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	125	105
International | Fixed income obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15	11
International | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	2
International | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	565	544
International | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	379	293
International | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	136	114
International | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61	55
International | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	916	877
International | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21	18
International | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,727	1,497
International | Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	70	50
International | Level 1 | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	546	461
International | Level 1 | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	66	56
International | Level 1 | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	462	372
International | Level 1 | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	4
International | Level 1 | Fixed income obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	7
International | Level 1 | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 1 | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	565	544
International | Level 1 | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	2
International | Level 1 | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
International | Level 1 | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 1 | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 1 | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,052	5,809
International | Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	3
International | Level 2 | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,761	3,071
International | Level 2 | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	96	112
International | Level 2 | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,534	2,082
International | Level 2 | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11	7
International | Level 2 | Fixed income obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	4
International | Level 2 | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
International | Level 2 | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 2 | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	376	291
International | Level 2 | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	135	113
International | Level 2 | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61	55
International | Level 2 | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	65	66
International | Level 2 | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	4
International | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	851	813	473
International | Level 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 3 | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 3 | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 3 | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 3 | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 3 | Fixed income obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 3 | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1	2
International | Level 3 | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 3 | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 3 | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 3 | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Level 3 | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	851	811	470
International | Level 3 | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1	$ 1
International | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	533	461
International | NAV | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15	16
International | NAV | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	96	75
International | NAV | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	90	83
International | NAV | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	207	180
International | NAV | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	109	94
International | NAV | Fixed income obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | NAV | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | NAV | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | NAV | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | NAV | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | NAV | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | NAV | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | NAV | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 16	$ 13

X

- Definition

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

+ References

No definition available.

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
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-Paragraph 1
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Reference 4: 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 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
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