v3.26.1
Fair Value (Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and cash equivalents $ 28,585 $ 24,365
Debt Securities, Available-for-sale 50,285 48,182
Equity Securities, FV-NI 2,206 2,170
Assets, Fair Value Disclosure 81,875 75,599
Loans Receivable, Fair Value Disclosure 799 882
Debt Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt Securities, Available-for-sale 50,285 48,182
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 3,047 3,932
State and Municipal Obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt Securities, Available-for-sale 5,551 6,325
Corporate Obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Debt Securities, Available-for-sale 28,261 25,546
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 10,268 9,719
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 3,158 2,660
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 15,784 19,848
Equity Securities, FV-NI 2,130 2,083
Assets, Fair Value Disclosure 20,875 25,709
Loans Receivable, Fair Value Disclosure 0 0
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 2,961 3,778
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 2,961 3,778
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 0 0
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 12,801 4,517
Equity Securities, FV-NI 0 20
Assets, Fair Value Disclosure 59,625 48,518
Loans Receivable, Fair Value Disclosure 0 0
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 46,824 43,981
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 86 154
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 5,551 6,325
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 27,761 25,123
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 10,268 9,719
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 3,158 2,660
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 76 67
Assets, Fair Value Disclosure 1,375 1,372
Loans Receivable, Fair Value Disclosure 799 882
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 500 423
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 500 423
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