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Comprehensive income - Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) to Net Income (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Beginning balance | $ 28,525 | $ 28,424 | $ 29,027 | $ 26,957
Other comprehensive income (loss), net of Tax, Portion attributable to parent | 62 | 524 | 441 | 432
Ending balance | 28,728 | 28,876 | 28,728 | 28,876
AOCI Attributable to Parent |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Equity, attributable to parent, beginning balance | 289 | (736) | (219) | (616)
Beginning balance | (74) | 185 | 55 | 157
Beginning balance | 215 | (551) | (164) | (459)
Other comprehensive income (loss) before reclassifications: | 64 | 600 | 490 | 284
Other comprehensive income (loss) before reclassifications, tax | (18) | (150) | (126) | (72)
OCI, before reclassifications, net of tax, attributable to parent | 46 | 450 | 364 | 212
Total other comprehensive income (loss) | 84 | 700 | 592 | 580
Deferred income taxes and credits | (22) | (176) | (151) | (148)
Other comprehensive income (loss), net of Tax, Portion attributable to parent | 62 | 524 | 441 | 432
Equity, attributable to parent, ending balance | 373 | (36) | 373 | (36)
Ending balance | (96) | 9 | (96) | 9
Ending balance | 277 | (27) | 277 | (27)
Investment Securities |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Equity, attributable to parent, beginning balance | 82 | (239) | (205) | (251)
Beginning balance | 61 | (179) | (153) | (187)
Other comprehensive income (loss) before reclassifications: | 81 | 308 | 368 | 307
Other comprehensive income (loss) before reclassifications, tax | (21) | (78) | (94) | (78)
OCI, before reclassifications, net of tax, attributable to parent | 60 | 230 | 274 | 229
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income: |  |  |  | 13
Reclassification from AOCI, current period, tax |  |  |  | (4)
Reclassification from AOCI, current period, net of tax, attributable to parent |  |  |  | 9
Total other comprehensive income (loss) | 81 | 308 | 368 | 320
Other comprehensive income (loss), net of Tax, Portion attributable to parent | 60 | 230 | 274 | 238
Equity, attributable to parent, ending balance | 163 | 69 | 163 | 69
Ending balance | 121 | 51 | 121 | 51
Cash Flow Hedges |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Equity, attributable to parent, beginning balance | 85 | (330) | (135) | (203)
Beginning balance | 63 | (246) | (101) | (151)
Other comprehensive income (loss) before reclassifications: | (16) | 287 | 118 | (26)
Other comprehensive income (loss) before reclassifications, tax | 3 | (71) | (31) | 7
OCI, before reclassifications, net of tax, attributable to parent | (13) | 216 | 87 | (19)
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income: | 22 | 102 | 108 | 288
Reclassification from AOCI, current period, tax | (4) | (27) | (26) | (73)
Reclassification from AOCI, current period, net of tax, attributable to parent | 18 | 75 | 82 | 215
Total other comprehensive income (loss) | 6 | 389 | 226 | 262
Other comprehensive income (loss), net of Tax, Portion attributable to parent | 5 | 291 | 169 | 196
Equity, attributable to parent, ending balance | 91 | 59 | 91 | 59
Ending balance | 68 | 45 | 68 | 45
Defined Benefit Plans |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Equity, attributable to parent, beginning balance | 127 | (158) | 131 | (155)
Beginning balance | 95 | (118) | 98 | (115)
Other comprehensive income (loss) before reclassifications: | 0 | 0 | 0 | 0
Total other comprehensive income (loss) | (2) | (2) | (6) | (5)
Other comprehensive income (loss), net of Tax, Portion attributable to parent | (2) | (1) | (5) | (4)
Equity, attributable to parent, ending balance | 125 | (160) | 125 | (160)
Ending balance | 93 | (119) | 93 | (119)
Prior Service Credit |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income: | (2) | (2) | (6) | (5)
Reclassification from AOCI, current period, tax | 0 | 1 | 1 | 1
Reclassification from AOCI, current period, net of tax, attributable to parent | (2) | (1) | (5) | (4)
Other |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Equity, attributable to parent, beginning balance | (5) | (9) | (10) | (7)
Beginning balance | (4) | (8) | (8) | (6)
Other comprehensive income (loss) before reclassifications: | (1) | 5 | 4 | 3
Other comprehensive income (loss) before reclassifications, tax | 0 | (1) | (1) | (1)
OCI, before reclassifications, net of tax, attributable to parent | (1) | 4 | 3 | 2
Total other comprehensive income (loss) | (1) | 5 | 4 | 3
Other comprehensive income (loss), net of Tax, Portion attributable to parent | (1) | 4 | 3 | 2
Equity, attributable to parent, ending balance | (6) | (4) | (6) | (4)
Ending balance | $ (5) | $ (4) | $ (5) | $ (4)

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