Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income Taxes
Effective tax rate of income (loss) before income taxes	22.20%	23.60%	21.00%	22.20%
Tax credits and adjustments	$ 49	$ 37	$ 138	$ 111
Low income housing investments [Member]
Income Taxes
Investment proportional amortization tax impact	26	19	71	56
Income tax benefit from low-income housing investments	37	26	99	76
Variable interest entities interest expense	8	$ 5	25	$ 16
Renewable Natural Gas [Member]
Income Taxes
Increase (decrease) to accruals and related deferred taxes	$ 22		$ 22

Amount, before amortization expense, of income tax credit and other tax benefit generated by investment under tax credit program elected to be accounted for using proportional amortization method. Includes, but is not limited to, investment under tax credit program not meeting condition for accounting under proportional amortization method.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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A credit or adjustment for government or taxing authority authorized decrease in taxes owed as a result of meeting certain tax policy conditions.

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Interest expense on beneficial interests issued by consolidated variable interest entities.

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Amount of income tax credit generated by investment under tax credit program elected to be accounted for using proportional amortization method. Includes, but is not limited to, investment under tax credit program not meeting condition for accounting under proportional amortization method.

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Income Taxes [Line Items]

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