Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative [Line Items]
Net gain/(loss) recognized in income	$ 6	$ 4	$ 25	$ (54)
Unrealized Gains Losses On Insured Derivatives [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income			0	(1)
Net gains (losses) on financial instruments at fair value and foreign exchange [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	5	6	22	(53)
Net gains (losses) on financial instruments at fair value and foreign exchange [Member] | Currency Swaps Vie [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	1	(1)	3	4
Net gains (losses) on financial instruments at fair value and foreign exchange [Member] | All Other [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	$ 0	$ (1)	$ 0	$ (4)