Derivative Instruments (Total Fair Value Of Company's Derivative Assets And Liabilities By Instrument And Balance Sheet Location, Before Counterparty Netting) (Detail) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative notional amount		$ 9,251	$ 9,859
Derivative Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	[1]	(456)	(406)
Derivative Assets [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	[1]	15	20
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative notional amount		1,155	1,153
Interest Rate Swap [Member] | Derivative Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	[1]	(282)	(240)
Interest Rate Swap [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	[1]	4	4
Credit Default Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative notional amount		2,851	3,208
Credit Default Swap [Member] | Derivative Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	[1]	(99)	(85)
Insured Swaps [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative notional amount		3,558	3,786
Insured Swaps [Member] | Derivative Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	[1]	(3)	(3)
Interest Rate Swaps V I E [Member]
Derivative [Line Items]
Derivative notional amount			899
Interest Rate Swaps V I E [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative notional amount		865
Interest Rate Swaps V I E [Member] | Derivative Liabilities V I E [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value			(45)
Interest Rate Swaps V I E [Member] | Derivative Liabilities V I E [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value		(36)
Interest Rate Swaps V I E [Member] | Derivative Assets V I E [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		0
Interest Rate Swaps Embedded [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative notional amount		415	396
Interest Rate Swaps Embedded [Member] | Medium Term Notes [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	[1]	5	5
Derivative Liabilities, Not designated, Fair Value	[1]	(17)	(15)
Currency Swaps Vie [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative notional amount		77	83
Currency Swaps Vie [Member] | Derivative Assets V I E [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value			11
Currency Swaps Vie [Member] | Derivative Assets V I E [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		6
All Other [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative notional amount		83	83
All Other [Member] | Derivative Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	[1]	(19)	(18)
All Other V I E [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative notional amount		241	241
All Other Embedded [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative notional amount		$ 6	$ 10

[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