| Financial Assets and Liabilities, Measured at Fair Value Recurring Basis [Table Text Block] |
The following table presents a summary of fair value measurements by level and carrying values for items measured at fair value on a recurring basis in the Condensed Consolidated Balance Sheets: | | | | | | | | | | | | | | | | | | | | | | | | | | | | (in millions) | | Quoted Prices
in Active
Markets
(Level 1) | | Other
Observable
Inputs
(Level 2) | | Unobservable
Inputs
(Level 3) | | Total
Fair and Carrying
Value | | June 30, 2025 | | | | | | | | | | Cash and cash equivalents | | $ | 23,299 | | $ | 5,297 | | $ | — | | $ | 28,596 | | Debt securities - available-for-sale: | | | | | | | | | | U.S. government and agency obligations | | 3,876 | | 130 | | — | | 4,006 | | State and municipal obligations | | — | | 6,866 | | — | | 6,866 | | Corporate obligations | | — | | 22,942 | | 473 | | 23,415 | | U.S. agency mortgage-backed securities | | — | | 9,566 | | — | | 9,566 | | Non-U.S. agency mortgage-backed securities | | — | | 2,755 | | — | | 2,755 | | Total debt securities - available-for-sale | | 3,876 | | 42,259 | | 473 | | 46,608 | | Equity securities | | 1,879 | | 213 | | 207 | | 2,299 | | Total assets at fair value | | $ | 29,054 | | $ | 47,769 | | $ | 680 | | $ | 77,503 | | Percentage of total assets at fair value | | 37 | % | | 62 | % | | 1 | % | | 100 | % | | December 31, 2024 | | | | | | | | | | Cash and cash equivalents | | $ | 25,248 | | $ | 64 | | $ | — | | $ | 25,312 | | Debt securities - available-for-sale: | | | | | | | | | | U.S. government and agency obligations | | 4,194 | | 133 | | — | | 4,327 | | State and municipal obligations | | — | | 6,984 | | — | | 6,984 | | Corporate obligations | | 29 | | 22,841 | | 437 | | 23,307 | | U.S. agency mortgage-backed securities | | — | | 9,584 | | — | | 9,584 | | Non-U.S. agency mortgage-backed securities | | — | | 2,717 | | — | | 2,717 | | Total debt securities - available-for-sale | | 4,223 | | 42,259 | | 437 | | 46,919 | | Equity securities | | 1,859 | | 24 | | 65 | | 1,948 | | Total assets at fair value | | $ | 31,330 | | $ | 42,347 | | $ | 502 | | $ | 74,179 | | Percentage of total assets at fair value | | 42 | % | | 57 | % | | 1 | % | | 100 | % |
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| Fair Value Measurements, Nonrecurring [Table Text Block] |
The following table presents a summary of fair value measurements by level and carrying values for certain financial instruments not measured at fair value on a recurring basis in the Condensed Consolidated Balance Sheets: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | (in millions) | | Quoted Prices
in Active
Markets
(Level 1) | | Other
Observable
Inputs
(Level 2) | | Unobservable
Inputs
(Level 3) | | Total
Fair
Value | | Total Carrying Value | | June 30, 2025 | | | | | | | | | | | | Debt securities - held-to-maturity | | $ | 466 | | | $ | 24 | | | $ | — | | | $ | 490 | | | $ | 493 | | | Long-term debt and other financing obligations | | $ | — | | | $ | 74,304 | | | $ | — | | | $ | 74,304 | | | $ | 79,193 | | | December 31, 2024 | | | | | | | | | | | | Debt securities - held-to-maturity | | $ | 482 | | | $ | 26 | | | $ | — | | | $ | 508 | | | $ | 512 | | | Long-term debt and other financing obligations | | $ | — | | | $ | 70,565 | | | $ | — | | | $ | 70,565 | | | $ | 75,604 | |
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