Income Taxes - Differences Between Statutory Income Tax Rate and Effective Income Tax Rate (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Increase (decrease) resulting from:
Tax at statutory rate	$ 161	$ (331)
Tax-exempt income from municipal bonds	(5)	(5)
Dividend received exclusion	(5)	(4)
Other	(3)	(10)
Total provision (benefit) for income taxes	$ 148	$ (350)
Increase (decrease) resulting from:
Tax at statutory rate	21.00%	21.00%
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent	(0.70%)	0.30%
Effective Income Tax Rate Reconciliation, Deduction, Dividend, Percent	(0.70%)	0.30%
Other	(0.30%)	0.60%
Provision for income taxes	19.30%	22.20%

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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