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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 | 6 Months Ended
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Jun. 30, 2024 | Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Beginning balance | $ 26,957 | $ 25,318
Ending balance | 28,424 | 25,801
AOCI Attributable to Parent |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Equity, attributable to parent, beginning balance | (616) | (1,066)
Beginning balance | 157 | 276
Beginning balance | (459) | (790)
Other comprehensive income (loss) before reclassifications: | (316) | (201)
Other comprehensive income (loss) before reclassifications, tax | 78 | 48
OCI, before reclassifications, net of tax, attributable to parent | (238) | (153)
Total other comprehensive income (loss) | (120) | (96)
Deferred income taxes and credits | 28 | 21
Other comprehensive income (loss), net of Tax, Portion attributable to parent | (92) | (75)
Equity, attributable to parent, ending balance | (736) | (1,162)
Ending balance | 185 | 297
Ending balance | (551) | (865)
Investment Securities |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Equity, attributable to parent, beginning balance | (251) | (444)
Beginning balance | (187) |
Other comprehensive income (loss) before reclassifications: | (1) | 3
Other comprehensive income (loss) before reclassifications, tax | 0 | (2)
OCI, before reclassifications, net of tax, attributable to parent | (1) | 1
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) | 12 | 3
Equity, attributable to parent, ending balance | (239) | (441)
Ending balance | (179) |
Cash Flow Hedges |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Equity, attributable to parent, beginning balance | (203) | (336)
Beginning balance | (151) |
Other comprehensive income (loss) before reclassifications: | (313) | (208)
Other comprehensive income (loss) before reclassifications, tax | 78 | 51
OCI, before reclassifications, net of tax, attributable to parent | (235) | (157)
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income: | 186 | 108
Reclassification from AOCI, current period, tax | (46) | (27)
Reclassification from AOCI, current period, net of tax, attributable to parent | 140 | 81
Total other comprehensive income (loss) | (127) | (100)
Equity, attributable to parent, ending balance | (330) | (436)
Ending balance | (246) |
Defined Benefit Plans |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Equity, attributable to parent, beginning balance | (155) | (273)
Beginning balance | (115) |
Other comprehensive income (loss) before reclassifications: | 0 | 0
Total other comprehensive income (loss) | (3) | (3)
Equity, attributable to parent, ending balance | (158) | (276)
Ending balance | (118) |
Prior Service Credit |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income: | (1) | (1)
Reclassification from AOCI, current period, tax | 0 | 0
Reclassification from AOCI, current period, net of tax, attributable to parent | (1) | (1)
Actuarial Gains |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Amounts reclassified from accumulated other comprehensive income (loss) that (increase) decrease net income: | (2) | (2)
Reclassification from AOCI, current period, tax | 0 | 0
Reclassification from AOCI, current period, net of tax, attributable to parent | (2) | (2)
Other |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Equity, attributable to parent, beginning balance | (7) | (13)
Beginning balance | (6) |
Other comprehensive income (loss) before reclassifications: | (2) | 4
Other comprehensive income (loss) before reclassifications, tax | 0 | (1)
OCI, before reclassifications, net of tax, attributable to parent | (2) | 3
Total other comprehensive income (loss) | (2) | 4
Equity, attributable to parent, ending balance | (9) | $ (9)
Ending balance | $ (8) |

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