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Earnings per common share - Computations of Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Earnings Per Share [Abstract] |  |  |  |
Net income available to common equity | $ 756 | $ 674 | $ 1,985 | $ 1,808
Less: Income attributable to unvested stock-based compensation awards | (2) | 0 | (4) | (3)
Net income available to common shareholders | $ 754 | $ 674 | $ 1,981 | $ 1,805
Adjusted weighted-average shares outstanding: |  |  |  |
Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards (in shares) | 155,885 | 167,011 | 159,956 | 167,010
Less: Unvested stock-based compensation awards (in shares) | (327) | (340) | (325) | (316)
Plus: Incremental shares from assumed conversion of stock-based compensation awards (in shares) | 995 | 896 | 872 | 743
Adjusted weighted-average shares outstanding (in shares) | 156,553 | 167,567 | 160,503 | 167,437
Diluted earnings per common share (in USD per share) | $ 4.82 | $ 4.02 | $ 12.34 | $ 10.78

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