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], USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Derivative [Line Items]
Derivative notional amount	$ 14,862		$ 15,839
Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(590)	[1]	(537)	[1]
Derivative Assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	14	[1]	91	[1]
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative notional amount	1,179		1,450
Interest Rate Swap [Member] | Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(269)	[1]	(248)	[1]
Interest Rate Swap [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	2	[1]	83	[1]
Credit Default Swap [Member]
Derivative [Line Items]
Derivative notional amount	8,086		9,481
Credit Default Swap [Member] | Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(207)	[1]	(244)	[1]
Insured Swaps [Member]
Derivative [Line Items]
Derivative notional amount	3,877		4,044
Insured Swaps [Member] | Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(3)	[1]	(2)	[1]
Interest Rate Swaps V I E [Member]
Derivative [Line Items]
Derivative notional amount	903
Interest Rate Swaps V I E [Member] | Derivative Liabilities V I E [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	76
Interest Rate Swaps Embedded [Member]
Derivative [Line Items]
Derivative notional amount	392		437
Interest Rate Swaps Embedded [Member] | Medium Term Notes [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	7	[1]	8	[1]
Derivative Liabilities, Not designated, Fair Value	(14)	[1]	(19)	[1]
Currency Swaps Vie [Member]
Derivative [Line Items]
Derivative notional amount	89		91
Currency Swaps Vie [Member] | Derivative Assets V I E [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	5
All Other [Member]
Derivative [Line Items]
Derivative notional amount	83		83
All Other [Member] | Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(21)	[1]	(24)	[1]
All Other V I E [Member]
Derivative [Line Items]
Derivative notional amount	241		241
All Other Embedded [Member]
Derivative [Line Items]
Derivative notional amount	$ 12		$ 12

[1] In accordance with the accounting guidance for derivative instruments and hedging activities, the balance sheet location of the Company's embedded derivative instruments is determined by the location of the related host contract