Income Taxes - Components of U.S. and Foreign Income and Reconciliation between Federal Income Tax Expense at Statutory Rates and Actual Income Tax Expense (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income before income tax:
Income before income tax, U.S.	$ 1,145	$ 775	$ 1,322
Income before income tax, Foreign	(26)	59	260
Income before income tax	1,119	834	1,582
Income tax expense at statutory rate	235	175	554
Increase (decrease) in income tax expense resulting from:
Effect of the Tax Act	(14)	(6)	(190)
Exempt investment income	(50)	(64)	(134)
Foreign related tax differential	(55)	1	(36)
Taxes related to domestic affiliate	(15)	(7)	1
Partnership earnings not subject to taxes		(14)	(51)
Valuation allowance	12	12	7
Unrecognized tax positions, settlements and adjustments relating to prior years	97	2	(8)
State taxes	37	20	23
Other	1	9	4
Income tax expense (benefit)	$ 248	$ 128	$ 170