Investments - Summary of Net Investment Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Investment [Line Items]
Net Realized and Unrealized Gain (Loss) on Trading Securities	$ (48)	$ 23	$ 0
Trading Securities, Realized Gain (Loss)	(26)	1	(18)
Fixed income securities		78	103
Investment expense	(6)	(6)	(6)
Securities available-for-sale and short-term	66	74	103
Net investment income	17	139	122
Gains (losses) on securities held as of reporting date [Member]
Investment [Line Items]
Other Investments Income	(22)	22	18
Available-for-sale Securities [Member]
Investment [Line Items]
Fixed income securities	61
Short-term Investments [Member]
Investment [Line Items]
Fixed income securities	11	0	5
Financing Receivable [Member]
Investment [Line Items]
Fixed income securities	1	0	1
Other Investments [Member]
Investment [Line Items]
Fixed income securities	(26)	$ 66	$ 19
Debt Securities, Trading
Investment [Line Items]
Fixed income securities	$ (23)