Amortized Cost or Cost, Gross Unrealized Gains (Losses) and Fair Value of Fixed Maturity and Equity Securities Classified as Available-for-Sale (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	$ 57,432
Fair value, fixed maturity securities	62,360	58,629
Fair value, equity securities	320	341
Amortized cost or cost, total	57,716	56,627
Fair value, total	62,680	58,970
Fixed maturity securities
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	57,432	56,309
Fair value, fixed maturity securities	62,360	58,629
Fixed maturity securities | U.S. government, agencies and government-sponsored enterprises
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	4,894	4,710
Fair value, fixed maturity securities	5,483	4,810
Fixed maturity securities | Tax-exempt
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	353	324
Fair value, fixed maturity securities	353	295
Fixed maturity securities | Government - non-U.S.
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	1,989	2,057
Fair value, fixed maturity securities	2,132	2,146
Fixed maturity securities | U.S. corporate
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	24,113	23,614
Fair value, fixed maturity securities	26,847	25,035
Fixed maturity securities | Corporate - non-U.S.
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	14,695	14,489
Fair value, fixed maturity securities	15,749	15,071
Fixed maturity securities | Residential mortgage-backed
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	4,923	5,058
Fair value, fixed maturity securities	5,212	5,225
Fixed maturity securities | Commercial mortgage-backed
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	2,721	2,886
Fair value, fixed maturity securities	2,845	2,898
Fixed maturity securities | Other asset-backed
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	3,744	3,171
Fair value, fixed maturity securities	3,739	3,149
Equity securities
Schedule of Investments [Line Items]
Amortized cost or cost, equity securities	284	318
Fair value, equity securities	320	341
Not other-than-temporary impairments
Schedule of Investments [Line Items]
Gross unrealized gains	5,266	3,319
Gross unrealized losses	(337)	(999)
Not other-than-temporary impairments | Fixed maturity securities
Schedule of Investments [Line Items]
Gross unrealized gains	5,226	3,283
Gross unrealized losses	(333)	(986)
Not other-than-temporary impairments | Fixed maturity securities | U.S. government, agencies and government-sponsored enterprises
Schedule of Investments [Line Items]
Gross unrealized gains	677	331
Gross unrealized losses	(88)	(231)
Not other-than-temporary impairments | Fixed maturity securities | Tax-exempt
Schedule of Investments [Line Items]
Gross unrealized gains	21	7
Gross unrealized losses	(21)	(36)
Not other-than-temporary impairments | Fixed maturity securities | Government - non-U.S.
Schedule of Investments [Line Items]
Gross unrealized gains	146	104
Gross unrealized losses	(3)	(15)
Not other-than-temporary impairments | Fixed maturity securities | U.S. corporate
Schedule of Investments [Line Items]
Gross unrealized gains	2,809	1,761
Gross unrealized losses	(94)	(359)
Not other-than-temporary impairments | Fixed maturity securities | Corporate - non-U.S.
Schedule of Investments [Line Items]
Gross unrealized gains	1,087	738
Gross unrealized losses	(33)	(156)
Not other-than-temporary impairments | Fixed maturity securities | Residential mortgage-backed
Schedule of Investments [Line Items]
Gross unrealized gains	309	232
Gross unrealized losses	(33)	(70)
Not other-than-temporary impairments | Fixed maturity securities | Commercial mortgage-backed
Schedule of Investments [Line Items]
Gross unrealized gains	138	75
Gross unrealized losses	(17)	(62)
Not other-than-temporary impairments | Fixed maturity securities | Other asset-backed
Schedule of Investments [Line Items]
Gross unrealized gains	39	35
Gross unrealized losses	(44)	(57)
Not other-than-temporary impairments | Equity securities
Schedule of Investments [Line Items]
Gross unrealized gains	40	36
Gross unrealized losses	(4)	(13)
Other-than-temporary impairments
Schedule of Investments [Line Items]
Gross unrealized gains	37	30
Gross unrealized losses	(2)	(7)
Other-than-temporary impairments | Fixed maturity securities
Schedule of Investments [Line Items]
Gross unrealized gains	37	30
Gross unrealized losses	(2)	(7)
Other-than-temporary impairments | Fixed maturity securities | U.S. government, agencies and government-sponsored enterprises
Schedule of Investments [Line Items]
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Other-than-temporary impairments | Fixed maturity securities | Tax-exempt
Schedule of Investments [Line Items]
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Other-than-temporary impairments | Fixed maturity securities | Government - non-U.S.
Schedule of Investments [Line Items]
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Other-than-temporary impairments | Fixed maturity securities | U.S. corporate
Schedule of Investments [Line Items]
Gross unrealized gains	19	19
Gross unrealized losses	0	0
Other-than-temporary impairments | Fixed maturity securities | Corporate - non-U.S.
Schedule of Investments [Line Items]
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Other-than-temporary impairments | Fixed maturity securities | Residential mortgage-backed
Schedule of Investments [Line Items]
Gross unrealized gains	14	9
Gross unrealized losses	(1)	(4)
Other-than-temporary impairments | Fixed maturity securities | Commercial mortgage-backed
Schedule of Investments [Line Items]
Gross unrealized gains	4	2
Gross unrealized losses	(1)	(3)
Other-than-temporary impairments | Fixed maturity securities | Other asset-backed
Schedule of Investments [Line Items]
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Other-than-temporary impairments | Equity securities
Schedule of Investments [Line Items]
Gross unrealized gains	0	0
Gross unrealized losses	$ 0	$ 0