Investments (Securities Held In Unrealized Loss Position And Insured By Financial Guarantor) (Detail) - Financial Guarantee [Member] $ in Millions	Jun. 30, 2022 USD ($)
Schedule Of Investments [Line Items]
Total available-for-sale, fair value	$ 196
Gross unrealized losses	(26)
Loss and loss adjustment expense reserves	125	[1]
Mortgage-backed [Member]
Schedule Of Investments [Line Items]
Total available-for-sale, fair value	110
Gross unrealized losses	(10)
Loss and loss adjustment expense reserves	125	[1]
Corporate Obligations [Member]
Schedule Of Investments [Line Items]
Total available-for-sale, fair value	86
Gross unrealized losses	(16)
Loss and loss adjustment expense reserves	$ 0	[1]

[1] Insurance loss reserve estimates are based on the proportion of par value owned to the total amount of par value insured and are discounted using a discount rate equal to the risk-free rate applicable to the currency and weighted average remaining life of the insurance contract and may differ from the fair value.