Derivative Instruments (Total Fair Value Of Company's Derivative Assets And Liabilities By Instrument And Balance Sheet Location, Before Counterparty Netting) (Detail) - Not Designated as Hedging Instrument [Member] - Derivative Instrument [Member] - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Derivative notional amount	$ 1,363	$ 1,766
Derivative Assets, Not designated, Fair Value	0	0
Derivative Liabilities, Not designated, Fair Value	(16)	(55)
Insured swaps [Member]
Derivative [Line Items]
Derivative notional amount	1,269	1,350
Insured swaps [Member] | Other assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	0	0
Insured swaps [Member] | Derivative liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(1)	0
Interest rate swaps [Member]
Derivative [Line Items]
Derivative notional amount	55	380
Interest rate swaps [Member] | Other assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	0	0
Interest rate swaps [Member] | Derivative liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(1)	(49)
Currency swaps-VIE [Member]
Derivative [Line Items]
Derivative notional amount	39	36
Currency swaps-VIE [Member] | Other assets-VIE [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	0	0
Currency swaps-VIE [Member] | Derivative liabilities-VIE [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	$ (14)	$ (6)