Investments - Summary of Net Investment Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investment [Line Items]
Trading Securities, Realized Gain (Loss)	$ 18	$ (26)	$ 1
Investment expense	(6)	(6)	(6)
Interest Income, Debt Securities, Available-for-Sale, Operating	93	66	74
Net investment income	140	17	139
Fixed income securities		61	78
Gains (losses) on securities held as of reporting date [Member]
Investment [Line Items]
Other Investments Income	7	(22)	22
Available-for-sale Securities [Member]
Investment [Line Items]
Fixed income securities	76
Short-term Investments [Member]
Investment [Line Items]
Fixed income securities	22	11	0
Financing Receivable [Member]
Investment [Line Items]
Fixed income securities	0	1	0
Other Investments [Member]
Investment [Line Items]
Fixed income securities	40	(26)	66
Debt Securities, Trading
Investment [Line Items]
Fixed income securities	$ 7	$ (23)	$ 0