Investments (Narrative) (Detail) $ in Millions	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) security	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) security
Schedule Of Investments [Line Items]
Fair value of securities on deposit with various regulatory authorities		$ 10		$ 10
Number of securities in unrealized loss position for a continuous 12 month period | security		597		210
Rate that a security's fair value is below book value		5.00%		5.00%
Increase decrease in other net realized (gains) losses		$ 17	$ 19
Asset Pledged as Collateral [Member]
Schedule Of Investments [Line Items]
Fair value of securities pledged as collateral		$ 233		$ 251
Securities In Unrealized Loss Position [Member]
Schedule Of Investments [Line Items]
Weighted average contractual maturity period in years for securities in an unrealized loss position		14 years		14 years
Increase decrease in other net realized (gains) losses	$ 19		$ 19
Fair Value Below Book Value Greater Than Five Percent [Member]
Schedule Of Investments [Line Items]
Number of securities in unrealized loss position for a continuous 12 month period | security		546		190