Activity Associated with Derivative Instruments (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Derivative [Line Items]
Notional amount, beginning balance	$ 22,640
Additions	13,029
Maturities/ terminations	(12,163)
Notional amount, end balance	23,506
Derivatives Designated As Hedges
Derivative [Line Items]
Notional amount, beginning balance	12,147
Additions	9,692
Maturities/ terminations	(6,571)
Notional amount, end balance	15,268
Derivatives Designated As Hedges | Cash Flow Hedges
Derivative [Line Items]
Notional amount, beginning balance	11,339
Additions	9,692
Maturities/ terminations	(5,768)
Notional amount, end balance	15,263
Derivatives Designated As Hedges | Cash Flow Hedges | Interest rate swaps
Derivative [Line Items]
Notional amount, beginning balance	10,146
Additions	9,586
Maturities/ terminations	(5,434)
Notional amount, end balance	14,298
Derivatives Designated As Hedges | Cash Flow Hedges | Inflation indexed swaps
Derivative [Line Items]
Notional amount, beginning balance	554
Additions	4
Maturities/ terminations	0
Notional amount, end balance	558
Derivatives Designated As Hedges | Cash Flow Hedges | Foreign currency swaps
Derivative [Line Items]
Notional amount, beginning balance	183
Additions	102
Maturities/ terminations	(250)
Notional amount, end balance	35
Derivatives Designated As Hedges | Cash Flow Hedges | Forward bond purchase commitments
Derivative [Line Items]
Notional amount, beginning balance	456
Additions	0
Maturities/ terminations	(84)
Notional amount, end balance	372
Derivatives Designated As Hedges | Fair value hedges
Derivative [Line Items]
Notional amount, beginning balance	808
Additions	0
Maturities/ terminations	(803)
Notional amount, end balance	5
Derivatives Designated As Hedges | Fair value hedges | Interest rate swaps
Derivative [Line Items]
Notional amount, beginning balance	723
Additions	0
Maturities/ terminations	(718)
Notional amount, end balance	5
Derivatives Designated As Hedges | Fair value hedges | Foreign currency swaps
Derivative [Line Items]
Notional amount, beginning balance	85
Additions	0
Maturities/ terminations	(85)
Notional amount, end balance	0
Derivatives not designated as hedges
Derivative [Line Items]
Notional amount, beginning balance	10,493
Additions	3,337
Maturities/ terminations	(5,592)
Notional amount, end balance	8,238
Derivatives not designated as hedges | GMWB embedded derivatives
Derivative [Line Items]
Notional amount, beginning balance	45,027
Additions	0
Maturities/ terminations	(1,499)
Notional amount, end balance	43,528
Derivatives not designated as hedges | Fixed index annuity embedded derivatives
Derivative [Line Items]
Notional amount, beginning balance	2,013
Additions	967
Maturities/ terminations	(7)
Notional amount, end balance	2,973
Derivatives not designated as hedges | Interest rate swaps
Derivative [Line Items]
Notional amount, beginning balance	6,331
Additions	254
Maturities/ terminations	(1,464)
Notional amount, end balance	5,121
Derivatives not designated as hedges | Interest rate swaps related to securitization entities
Derivative [Line Items]
Notional amount, beginning balance	104
Additions	0
Maturities/ terminations	(6)
Notional amount, end balance	98
Derivatives not designated as hedges | Credit default swaps
Derivative [Line Items]
Notional amount, beginning balance	932
Additions	69
Maturities/ terminations	(278)
Notional amount, end balance	723
Derivatives not designated as hedges | Credit default swaps related to securitization entities
Derivative [Line Items]
Notional amount, beginning balance	312
Additions	0
Maturities/ terminations	0
Notional amount, end balance	312
Derivatives not designated as hedges | Equity index options
Derivative [Line Items]
Notional amount, beginning balance	936
Additions	313
Maturities/ terminations	(710)
Notional amount, end balance	539
Derivatives not designated as hedges | Financial futures
Derivative [Line Items]
Notional amount, beginning balance	1,692
Additions	2,456
Maturities/ terminations	(3,120)
Notional amount, end balance	1,028
Derivatives not designated as hedges | Equity return swaps
Derivative [Line Items]
Notional amount, beginning balance	186
Additions	28
Maturities/ terminations	0
Notional amount, end balance	214
Derivatives not designated as hedges | Other foreign currency contracts
Derivative [Line Items]
Notional amount, beginning balance	0
Additions	217
Maturities/ terminations	(14)
Notional amount, end balance	$ 203