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Fair Value Measurements - Summary of Changes in Level 3 Fair Value Category (Details) $ in Millions | 3 Months Ended |  |
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Mar. 31, 2021 USD ($) level3FinancialInstruments | Mar. 31, 2020 USD ($) level3FinancialInstruments | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis Asset or Liability, Transfers into or out of Level 3 | level3FinancialInstruments | 0 | 0 |  |
Interest Rate Swap [Member] | Interest Rate Swap [Member] |  |  |  |
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability | $ 66 | $ 79 | $ 85 | $ 67
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) | (17) | 13 |  |
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI | (17) | 0 |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings | (17) | 13 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements | (2) | (1) |  |
Credit Derivative [Member] | Credit Derivative [Member] |  |  |  |
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability | 0 | (2) | 0 | 0
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) | 0 | (2) |  |
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI | 0 | 0 |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings | 0 | (1) |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements | 0 | 0 |  |
Derivative [Member] |  |  |  |
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability | 65 | 77 | 84 | 66
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) | (17) | 12 |  |
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI | (17) | 0 |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings | (17) | 12 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements | (2) | (1) |  |
Level 3 [Member] |  |  |  |
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability | 6,194 | 5,884 | 6,376 | 6,207
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) | (145) | 130 |  |
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI | 49 | (377) |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings | (145) | 130 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss | 49 | (377) |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements | (86) | (76) |  |
Level 3 [Member] | Loans Receivable [Member] | Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability | 2,948 | 2,932 | 2,998 | 3,108
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) | 9 | 88 |  |
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI | 24 | (190) |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings | 9 | 88 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss | 24 | (190) |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements | (84) | (74) |  |
Level 3 [Member] | Investments [Member] |  |  |  |
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability | 76 | 66 | 78 | 72
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI | (2) | (6) |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings | 0 | 0 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss | (2) | (6) |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements | 0 | 0 |  |
Level 3 [Member] | Other Assets [Member] |  |  |  |
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability | 1 | 3 | 1 | 3
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) | 0 | 0 |  |
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI | 0 | 0 |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings | 0 | 0 |  |
Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] |  |  |  |
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability | 65 | 77 | 84 | 66
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) | (17) | 12 |  |
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI | 0 | 0 |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings | (17) | 12 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements | (2) | (1) |  |
Level 3 [Member] | Corporate Debt Securities [Member] | Investment Contracts [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability | 3,103 | 2,806 | $ 3,215 | $ 2,957
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) | (138) | 30 |  |
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI | 26 | (181) |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings | (138) | 30 |  |
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss | $ 26 | $ (181) |  |

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- Definition Amount of gain or loss included in earnings arising from financial instruments measured on a recurring basis using unobservable inputs. + References No definition available. + Details
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- Definition Amount of gain or loss included in other comprehensive income arising from financial instruments measured on a recurring basis using unobservable inputs. + References No definition available. + Details
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- Definition Amount of unrealized gain (loss) recognized in income from asset (liability) measured at fair value on recurring basis using unobservable input (level 3) and still held. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Definition Amount of unrealized gain (loss) recognized in other comprehensive income (OCI) from asset (liability) measured at fair value on recurring basis using unobservable input (level 3) and still held. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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