Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative [Line Items]
Net gain/(loss) recognized in income	$ (19)	$ (8)	$ 18	$ (58)
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	(18)	(3)	17	(59)
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)	$ (5)	1	5
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	$ (3)