Income Taxes - Differences Between Statutory Income Tax Rate and Effective Income Tax Rate (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Increase (decrease) resulting from:
Tax at statutory rate	$ 129	$ 62	$ 38	$ 355
Tax-exempt income from municipal bonds	(5)	(5)	(15)	(14)
Dividend received exclusion	(5)	(3)	(13)	(11)
Other	11	(8)	6	(10)
Total provision for income taxes	$ 130	$ 46	$ 16	$ 320
Increase (decrease) resulting from:
Tax at statutory rate	21.00%	21.00%	21.00%	21.00%
Tax-exempt income from municipal bonds	(0.80%)	(1.70%)	(8.20%)	(0.80%)
Dividend received exclusion	(0.80%)	(1.00%)	(7.10%)	(0.70%)
Other	1.80%	(2.70%)	3.00%	(0.60%)
Provision for income taxes	21.20%	15.60%	8.70%	18.90%

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

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for dividend.

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

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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