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Fair Value (Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | $ 21,085 | $ 16,921
Debt Securities, Available-for-sale | 42,757 | 39,828
Equity Securities, FV-NI | 2,058 | 1,828
Assets under management | 4,304 | 4,076
Assets, Fair Value Disclosure | 70,204 | 62,653
Debt Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 42,757 | 39,828
U.S. Government and Agency Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 3,672 | 3,465
State and Municipal Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 7,419 | 7,328
Corporate Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 22,450 | 19,737
U.S. Agency Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 6,403 | 7,091
Non-U.S. Agency Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 2,813 | 2,207
Quoted Prices in Active Markets (Level 1) [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 20,944 | 16,841
Equity Securities, FV-NI | 1,972 | 1,795
Assets under management | 1,930 | 1,774
Assets, Fair Value Disclosure | 28,354 | 23,676
Quoted Prices in Active Markets (Level 1) [Member] | Debt Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 3,508 | 3,266
Quoted Prices in Active Markets (Level 1) [Member] | U.S. Government and Agency Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 3,446 | 3,241
Quoted Prices in Active Markets (Level 1) [Member] | State and Municipal Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 0 | 0
Quoted Prices in Active Markets (Level 1) [Member] | Corporate Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 62 | 25
Quoted Prices in Active Markets (Level 1) [Member] | U.S. Agency Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 0 | 0
Quoted Prices in Active Markets (Level 1) [Member] | Non-U.S. Agency Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 0 | 0
Other Observable Inputs (Level 2) [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 141 | 80
Equity Securities, FV-NI | 22 | 33
Assets under management | 2,271 | 2,250
Assets, Fair Value Disclosure | 41,460 | 38,637
Other Observable Inputs (Level 2) [Member] | Debt Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 39,026 | 36,274
Other Observable Inputs (Level 2) [Member] | U.S. Government and Agency Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 226 | 224
Other Observable Inputs (Level 2) [Member] | State and Municipal Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 7,419 | 7,328
Other Observable Inputs (Level 2) [Member] | Corporate Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 22,165 | 19,424
Other Observable Inputs (Level 2) [Member] | U.S. Agency Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 6,403 | 7,091
Other Observable Inputs (Level 2) [Member] | Non-U.S. Agency Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 2,813 | 2,207
Unobservable Inputs (Level 3) [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 0 | 0
Equity Securities, FV-NI | 64 | 0
Assets under management | 103 | 52
Assets, Fair Value Disclosure | 390 | 340
Unobservable Inputs (Level 3) [Member] | Debt Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 223 | 288
Unobservable Inputs (Level 3) [Member] | U.S. Government and Agency Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 0 | 0
Unobservable Inputs (Level 3) [Member] | State and Municipal Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 0 | 0
Unobservable Inputs (Level 3) [Member] | Corporate Obligations [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 223 | 288
Unobservable Inputs (Level 3) [Member] | U.S. Agency Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | 0 | 0
Unobservable Inputs (Level 3) [Member] | Non-U.S. Agency Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Securities, Available-for-sale | $ 0 | $ 0

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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
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