Income Taxes - Differences Between Statutory Income Tax Rate and Effective Income Tax Rate (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Increase (decrease) resulting from:
Tax at statutory rate	$ (218)	$ 183	$ (294)	$ 344
Tax-exempt income from municipal bonds	(5)	(5)	(10)	(10)
Dividend received exclusion	(5)	(4)	(10)	(9)
Other	(5)	(5)	(6)	(8)
Total provision (benefit) for income taxes	$ (233)	$ 169	$ (320)	$ 317
Increase (decrease) resulting from:
Tax at statutory rate	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent	0.50%	(0.60%)	0.70%	(0.60%)
Effective Income Tax Rate Reconciliation, Deduction, Dividend, Percent	0.50%	(0.50%)	0.70%	(0.50%)
Other	0.40%	(0.50%)	0.40%	(0.60%)
Provision for income taxes	22.40%	19.40%	22.80%	19.30%