Income Taxes - Difference Between Effective Tax Rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal income tax at U.S. statutory rate	$ (584)	$ (1,357)	$ 9
Foreign income tax rate differential	(30)	(40)	(3)
Goodwill impairment	271	666
Reduction of FTC carryforwards	184
Tax Benefit from CARES Act	(83)
Change in deferred tax valuation allowance	(83)	218	49
Nondeductible expenses	44	61	20
Foreign dividends, net of foreign tax credits	28	163	27
Change in uncertain tax positions	20	(60)	(5)
Prior years taxes	(6)	3	(13)
State income taxes - net of federal benefit	(4)	(16)	(3)
Other	1	(7)	(18)
Total income tax provision	$ (242)	$ (369)	$ 63