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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 | 6 Months Ended
--- | --- | ---
Jun. 30, 2026 | Jun. 30, 2025 | Jun. 30, 2026 | Jun. 30, 2025
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Beginning balance | $ 27,972 | $ 28,991 | $ 29,177 | $ 29,027
Other comprehensive income (loss), net of Tax, Portion attributable to parent | (158) | 125 | (369) | 379
Ending balance | 27,946 | 28,525 | 27,946 | 28,525
AOCI Attributable to Parent |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Equity, attributable to parent, beginning balance | 90 | 121 | 372 | (219)
Beginning balance | (24) | (31) | (95) | 55
Beginning balance | 66 | 90 | 277 | (164)
OCI, before Reclassifications, before Tax, Attributable to Parent | (203) | 137 | (475) | 426
Other comprehensive income (loss) before reclassifications, tax | 51 | (35) | 120 | (108)
OCI, before reclassifications, net of tax, attributable to parent | (152) | 102 | (355) | 318
Total other comprehensive income (loss) | (213) | 168 | (495) | 508
Deferred income taxes and credits | 55 | (43) | 126 | (129)
Other comprehensive income (loss), net of Tax, Portion attributable to parent | (158) | 125 | (369) | 379
Equity, attributable to parent, ending balance | (123) | 289 | (123) | 289
Ending balance | 31 | (74) | 31 | (74)
Ending balance | (92) | 215 | (92) | 215
Investment Securities |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Equity, attributable to parent, beginning balance | 9 | (8) | 208 | (205)
Beginning balance | 6 | (6) | 155 | (153)
OCI, before Reclassifications, before Tax, Attributable to Parent | (134) | 90 | (329) | 287
Other comprehensive income (loss) before reclassifications, tax | 35 | (23) | 84 | (73)
OCI, before reclassifications, net of tax, attributable to parent | (99) | 67 | (245) | 214
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income: |  |  | (4) |
Reclassification from AOCI, current period, tax |  |  | 1 |
Reclassification from AOCI, current period, net of tax, attributable to parent |  |  | (3) |
Total other comprehensive income (loss) | (134) | 90 | (333) | 287
Other comprehensive income (loss), net of Tax, Portion attributable to parent | (99) | 67 | (248) | 214
Equity, attributable to parent, ending balance | (125) | 82 | (125) | 82
Ending balance | (93) | 61 | (93) | 61
Cash Flow Hedges |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Equity, attributable to parent, beginning balance | 9 | 9 | 90 | (135)
Beginning balance | 7 | 7 | 67 | (101)
OCI, before Reclassifications, before Tax, Attributable to Parent | (69) | 43 | (145) | 134
Other comprehensive income (loss) before reclassifications, tax | 16 | (11) | 36 | (34)
OCI, before reclassifications, net of tax, attributable to parent | (53) | 32 | (109) | 100
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income: | (8) | 33 | (13) | 86
Reclassification from AOCI, current period, tax | 3 | (9) | 4 | (22)
Reclassification from AOCI, current period, net of tax, attributable to parent | (5) | 24 | (9) | 64
Total other comprehensive income (loss) | (77) | 76 | (158) | 220
Other comprehensive income (loss), net of Tax, Portion attributable to parent | (58) | 56 | (118) | 164
Equity, attributable to parent, ending balance | (68) | 85 | (68) | 85
Ending balance | (51) | 63 | (51) | 63
Defined Benefit Plans |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Equity, attributable to parent, beginning balance | 80 | 129 | 81 | 131
Beginning balance | 60 | 96 | 61 | 98
OCI, before Reclassifications, before Tax, Attributable to Parent | 0 | 0 | 0 | 0
Total other comprehensive income (loss) | (2) | (2) | (3) | (4)
Other comprehensive income (loss), net of Tax, Portion attributable to parent | (1) | (1) | (2) | (3)
Equity, attributable to parent, ending balance | 78 | 127 | 78 | 127
Ending balance | 59 | 95 | 59 | 95
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) | (3) | (4)
Reclassification from AOCI, current period, tax | 1 | 1 | 1 | 1
Reclassification from AOCI, current period, net of tax, attributable to parent | (1) | (1) | (2) | (3)
Other |  |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |  |
Equity, attributable to parent, beginning balance | (8) | (9) | (7) | (10)
Beginning balance | (7) | (7) | (6) | (8)
OCI, before Reclassifications, before Tax, Attributable to Parent | 0 | 4 | (1) | 5
Other comprehensive income (loss) before reclassifications, tax |  | (1) | 0 | (1)
OCI, before reclassifications, net of tax, attributable to parent |  | 3 | (1) | 4
Total other comprehensive income (loss) | 0 | 4 | (1) | 5
Other comprehensive income (loss), net of Tax, Portion attributable to parent | 0 | 3 | (1) | 4
Equity, attributable to parent, ending balance | (8) | (5) | (8) | (5)
Ending balance | $ (7) | $ (4) | $ (7) | $ (4)

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