Investments (Available for Sale in Consolidated Investment Portfolio) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Schedule of Investments [Line Items]
Amortized Cost	$ 7,306		$ 9,025
Gross Unrealized Gains	314		263
Gross unrealized losses, available for sale securities	(226)		(478)
Fair Value	7,394		8,810
Other-Than- Temporary Impairments	(173)	[1]	(233)	[1]
Total Other Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	695		1,060
Gross Unrealized Gains			1
Gross unrealized losses, available for sale securities	(1)		(19)
Fair Value	694		1,042
Fixed-Maturity Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	6,044		7,492
Gross Unrealized Gains	304		262
Gross unrealized losses, available for sale securities	(185)		(418)
Fair Value	6,163		7,336
Other-Than- Temporary Impairments	(173)	[1]	(233)	[1]
Fixed-Maturity Investments [Member] | Variable Interest Entity [Member]
Schedule of Investments [Line Items]
Amortized Cost	458
Fair Value	428
Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	1,275
Fair Value	1,294
Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member] | Variable Interest Entity [Member]
Schedule of Investments [Line Items]
Amortized Cost	106
Fair Value	87
Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	396
Fair Value	293
Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member] | Variable Interest Entity [Member]
Schedule of Investments [Line Items]
Amortized Cost	138
Fair Value	125
Corporate Obligations [Member] | Variable Interest Entity [Member]
Schedule of Investments [Line Items]
Amortized Cost	177		2
Gross Unrealized Gains	6
Gross unrealized losses, available for sale securities	(7)
Fair Value	176		2
Residential Mortgage-Backed Non-Agency [Member] | Mortgage-Backed Securities [Member] | Variable Interest Entity [Member]
Schedule of Investments [Line Items]
Amortized Cost	106		119
Gross unrealized losses, available for sale securities	(19)		(26)
Fair Value	87		93
Collateralized Debt Obligations [Member] | Asset-Backed Securities [Member] | Variable Interest Entity [Member]
Schedule of Investments [Line Items]
Amortized Cost	109		112
Gross unrealized losses, available for sale securities	(14)		(15)
Fair Value	95		97
Other Asset-Backed [Member] | Asset-Backed Securities [Member] | Variable Interest Entity [Member]
Schedule of Investments [Line Items]
Amortized Cost	29		41
Gross Unrealized Gains	1
Fair Value	30		41
State And Municipal Bonds [Member] | Variable Interest Entity [Member]
Schedule of Investments [Line Items]
Amortized Cost	37
Gross Unrealized Gains	3
Fair Value	40
Perpetual Preferred Securities [Member] | Total Other Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	50		127
Gross unrealized losses, available for sale securities	(1)		(19)
Fair Value	49		108
Other Investment Securities | Total Other Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	10		22
Gross Unrealized Gains			1
Fair Value	10		23
Money Market Securities [Member] | Total Other Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	635		911
Fair Value	635		911
Money Market Securities [Member] | Total Other Investments [Member] | Variable Interest Entity [Member]
Schedule of Investments [Line Items]
Amortized Cost	109		199
Fair Value	109		199
Taxable Bonds [Member] | Fixed-Maturity Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,032		6,370
Gross Unrealized Gains	248		221
Gross unrealized losses, available for sale securities	(184)		(416)
Fair Value	5,096		6,175
Other-Than- Temporary Impairments	(173)	[1]	(233)	[1]
Taxable Bonds [Member] | U.S. Treasury And Government Agency [Member] | Fixed-Maturity Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	1,036		1,091
Gross Unrealized Gains	49		39
Fair Value	1,085		1,130
Taxable Bonds [Member] | Foreign Governments [Member] | Fixed-Maturity Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	328		326
Gross Unrealized Gains	22		23
Fair Value	350		349
Taxable Bonds [Member] | Corporate Obligations [Member] | Fixed-Maturity Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	1,111		1,698
Gross Unrealized Gains	50		43
Gross unrealized losses, available for sale securities	(24)		(106)
Fair Value	1,137		1,635
Other-Than- Temporary Impairments	(2)	[1]	(2)	[1]
Taxable Bonds [Member] | Residential Mortgage-Backed Agency [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	1,032		1,198
Gross Unrealized Gains	47		47
Fair Value	1,079		1,245
Taxable Bonds [Member] | Residential Mortgage-Backed Non-Agency [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	199		325
Gross Unrealized Gains	15		31
Gross unrealized losses, available for sale securities	(39)		(83)
Fair Value	175		273
Other-Than- Temporary Impairments	(113)	[1]	(125)	[1]
Taxable Bonds [Member] | Commercial Mortgage-Backed [Member] | Fixed-Maturity Investments [Member] | Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	44		58
Gross Unrealized Gains	1		1
Gross unrealized losses, available for sale securities	(5)		(10)
Fair Value	40		49
Taxable Bonds [Member] | Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	184		251
Gross unrealized losses, available for sale securities	(86)		(118)
Fair Value	98		133
Other-Than- Temporary Impairments	(57)	[1]	(69)	[1]
Taxable Bonds [Member] | Other Asset-Backed [Member] | Fixed-Maturity Investments [Member] | Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	212		520
Gross Unrealized Gains	2		2
Gross unrealized losses, available for sale securities	(19)		(82)
Fair Value	195		440
Other-Than- Temporary Impairments	(1)	[1]	(37)	[1]
Taxable Bonds [Member] | State And Municipal Bonds [Member] | Fixed-Maturity Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	886		903
Gross Unrealized Gains	62		35
Gross unrealized losses, available for sale securities	(11)		(17)
Fair Value	937		921
Tax-Exempt Bonds [Member] | State And Municipal Bonds [Member] | Fixed-Maturity Investments [Member]
Schedule of Investments [Line Items]
Amortized Cost	1,012		1,122
Gross Unrealized Gains	56		41
Gross unrealized losses, available for sale securities	(1)		(2)
Fair Value	$ 1,067		$ 1,161

[1] Represents the amount of other-than-temporary losses recognized in accumulated other comprehensive income (loss) since the adoption of the accounting guidance for other-than-temporary impairments.