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Pension and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Millions |  | 1 Months Ended | 3 Months Ended | 9 Months Ended
--- | --- | --- | --- | ---
Mar. 11, 2021 | Oct. 31, 2021 | Sep. 30, 2021 | Mar. 31, 2021 | Sep. 30, 2020 | Jun. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Restructuring and other charges |  |  | $ 8 |  | $ 22 |  | $ 22 | $ 166
Settlement charges |  |  | (3) |  | (3) |  | (9) | (67)
Pension benefits |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Restructuring and other charges |  |  | 3 |  | 8 |  | 9 | 10
Increase (decrease) in minimum required pension funding | $ 120 |  |  |  |  |  |  |
Settlement charges |  |  | (3) |  | (8) |  | (9) | (72)
Pension benefits | UK |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Settlement charges |  |  |  |  |  | $ 62 |  | 62
Pension benefits | Subsequent Event |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Restructuring and other charges |  | $ 30 |  |  |  |  |  |
Increase (decrease) in obligation, pension benefits |  | $ 125 |  |  |  |  |  |
Other postretirement benefits |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Increase (decrease) in obligation, pension benefits |  |  |  | $ 39 |  |  |  |
Curtailments |  |  | $ 0 |  | $ 2 |  | $ 0 | $ 2
Other postretirement benefits | US |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Increase (decrease) in obligation, pension benefits |  |  |  |  |  | $ 6 |  |

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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from event reducing expected years of future service of present employees or eliminating accrual of defined benefits for some or all future services of present employees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -URI http://asc.fasb.org/extlink&oid=123453770&loc=SL108413299-114919 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(7) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(7) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920 + Details
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