Income Taxes - Provision for Federal & Foreign Income Tax Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current
Operations	$ 698	$ 975	$ (189)
One-time charge due to tax legislation	0	(6)	43
Deferred
Operations	235	(194)	1,607
One-time charge due to tax legislation	0	(37)	1,843
Total federal income tax expense	933	738	3,304
Foreign income tax expense (benefit):
Current	91	67	53
Deferred	(13)	(13)	(1)
Total foreign income tax expense	78	54	52
Total income tax expense	$ 1,011	$ 792	$ 3,356