Credit Losses Recognized in Net Income (Loss) on Debt Securities (Detail) - Debt Securities - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Cumulative credit losses, beginning balance	$ 24	$ 32
Securities sold, paid down or disposed	(2)	(8)
Cumulative credit losses, ending balance	$ 22	$ 24