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Derivative Financial Instruments - Balance Sheet Location of Cumulative Basis Adjustments (Details) - Fair Value Hedges - GM Financial - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
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Derivatives, Fair Value [Line Items] |  |
Carrying Amount of Hedged Items | $ 23,315 | $ 20,397
Cumulative Amount of Fair Value Hedging Adjustments | (739) | (77)
Short-term Debt |  |
Derivatives, Fair Value [Line Items] |  |
Carrying Amount of Hedged Items | 4,858 | 996
Cumulative Amount of Fair Value Hedging Adjustments | (69) | 4
Long-term Debt |  |
Derivatives, Fair Value [Line Items] |  |
Carrying Amount of Hedged Items | 18,457 | 19,401
Cumulative Amount of Fair Value Hedging Adjustments | (670) | $ (81)
Cumulative fair value adjustment on discontinued hedging relationships | $ 200 |

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- Definition Amount of liability hedged in fair value hedging relationship. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4EE -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109999712-113959 + Details
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