Income Taxes - Differences Between Statutory Income Tax Rate and Effective Income Tax Rate (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Increase (decrease) resulting from:
Tax at statutory rate	$ (76)	$ 161
Tax-exempt income from municipal bonds	(5)	(5)
Dividend received exclusion	(5)	(5)
Other	(1)	(3)
Total provision (benefit) for income taxes	$ (87)	$ 148
Increase (decrease) resulting from:
Tax at statutory rate	21.00%	21.00%
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent	1.40%	(0.70%)
Effective Income Tax Rate Reconciliation, Deduction, Dividend, Percent	1.40%	(0.70%)
Other	0.40%	(0.30%)
Provision for income taxes	24.20%	19.30%