Activity Associated with Derivative Instruments (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) Policies
Derivative [Line Items]
Notional amount, beginning balance	$ 23,912
Additions	11,828
Maturities/ terminations	(12,433)
Notional amount, ending balance	23,307
Designated As Hedging Instrument
Derivative [Line Items]
Notional amount, beginning balance	11,592
Additions	391
Maturities/ terminations	(806)
Notional amount, ending balance	11,177
Designated As Hedging Instrument | Cash Flow Hedges
Derivative [Line Items]
Notional amount, beginning balance	11,592
Additions	391
Maturities/ terminations	(806)
Notional amount, ending balance	11,177
Designated As Hedging Instrument | Cash Flow Hedges | Interest rate swaps
Derivative [Line Items]
Notional amount, beginning balance	11,570
Additions	391
Maturities/ terminations	(806)
Notional amount, ending balance	11,155
Designated As Hedging Instrument | Cash Flow Hedges | Foreign currency swaps
Derivative [Line Items]
Notional amount, beginning balance	22
Additions	0
Maturities/ terminations	0
Notional amount, ending balance	22
Derivatives not designated as hedges
Derivative [Line Items]
Notional amount, beginning balance	12,320
Additions	11,437
Maturities/ terminations	(11,627)
Notional amount, ending balance	12,130
Derivatives not designated as hedges | Interest rate swaps
Derivative [Line Items]
Notional amount, beginning balance	4,679
Additions	0
Maturities/ terminations	0
Notional amount, ending balance	4,679
Derivatives not designated as hedges | Foreign currency swaps
Derivative [Line Items]
Notional amount, beginning balance	201
Additions	167
Maturities/ terminations	(19)
Notional amount, ending balance	349
Derivatives not designated as hedges | Credit default swaps
Derivative [Line Items]
Notional amount, beginning balance	39
Additions	0
Maturities/ terminations	0
Notional amount, ending balance	39
Derivatives not designated as hedges | Credit default swaps related to securitization entities
Derivative [Line Items]
Notional amount, beginning balance	312	[1]
Additions	0	[1]
Maturities/ terminations	(312)	[1]
Notional amount, ending balance	0	[1]
Derivatives not designated as hedges | Equity index options
Derivative [Line Items]
Notional amount, beginning balance	2,396
Additions	2,982
Maturities/ terminations	(2,958)
Notional amount, ending balance	2,420
Derivatives not designated as hedges | Financial futures
Derivative [Line Items]
Notional amount, beginning balance	1,398
Additions	5,639
Maturities/ terminations	(5,754)
Notional amount, ending balance	1,283
Derivatives not designated as hedges | Equity return swaps
Derivative [Line Items]
Notional amount, beginning balance	165
Additions	265
Maturities/ terminations	(334)
Notional amount, ending balance	96
Derivatives not designated as hedges | Other foreign currency contracts
Derivative [Line Items]
Notional amount, beginning balance	3,130
Additions	2,384
Maturities/ terminations	(2,250)
Notional amount, ending balance	$ 3,264
Derivatives not designated as hedges | GMWB embedded derivatives
Derivative [Line Items]
Notional amount, beginning balance | Policies	33,238
Additions | Policies	0
Maturities/ terminations | Policies	(2,788)
Notional amount, ending balance | Policies	30,450
Derivatives not designated as hedges | Fixed index annuity embedded derivatives
Derivative [Line Items]
Notional amount, beginning balance | Policies	17,549
Additions | Policies	0
Maturities/ terminations | Policies	(482)
Notional amount, ending balance | Policies	17,067
Derivatives not designated as hedges | Indexed universal life embedded derivatives
Derivative [Line Items]
Notional amount, beginning balance | Policies	1,074
Additions | Policies	1
Maturities/ terminations | Policies	(90)
Notional amount, ending balance | Policies	985

[1] See note 17 for additional information related to consolidated securitization entities.