Derivative Financial Instruments and Off-balance sheet Financial Instruments (Details) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012 contract	Dec. 31, 2011 contract
Derivative Financial Instruments and Off-balance sheet Financial Instruments
Cash and securities pledged in the form of margin deposits	$ 11
Derivatives, Fair Value
Total asset derivatives, Notional amount	7,961	13,811
Total liability derivatives, Notional amount	8,218	9,046
Total derivatives, Notional amount	16,179	22,857
Total asset derivatives, Number of contracts	13,489	17,352
Total liability derivatives, Number of contracts	12,619	15,677
Total derivatives, Number of contracts	26,108	33,029
Total asset derivatives, Fair value, net	158	105
Asset derivatives, Gross asset	182	273
Asset derivatives, Gross liability	(24)	(168)
Total liability derivatives, Fair value, net	(646)	(857)
Total derivatives, Fair value, net	(488)	(752)
Liability derivatives, Gross asset	23	22
Liability derivatives, Gross liability	(669)	(879)
Number of stock rights held by the company related to derivative contracts (in shares)	34,634	10,798
Number of stock warrants held by the company related to derivative contracts (in shares)	879,158	4,392,937
Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	16	271
Total liability derivatives, Notional amount	135	78
Total asset derivatives, Fair value, net	2	(13)
Asset derivatives, Gross asset	2	3
Asset derivatives, Gross liability		(16)
Total liability derivatives, Fair value, net	(19)	(12)
Liability derivatives, Gross liability	(19)	(12)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	7,945	13,540
Total liability derivatives, Notional amount	8,083	8,968
Total asset derivatives, Number of contracts	13,489	17,352
Total liability derivatives, Number of contracts	12,619	15,677
Total asset derivatives, Fair value, net	156	118
Asset derivatives, Gross asset	180	270
Asset derivatives, Gross liability	(24)	(152)
Total liability derivatives, Fair value, net	(627)	(845)
Liability derivatives, Gross asset	23	22
Liability derivatives, Gross liability	(650)	(867)
Interest rate swap agreements | Other investments | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		144
Total asset derivatives, Fair value, net		(8)
Asset derivatives, Gross liability		(8)
Interest rate swap agreements | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	5,541	8,028
Total asset derivatives, Fair value, net	19	122
Asset derivatives, Gross asset	28	137
Asset derivatives, Gross liability	(9)	(15)
Interest rate swap agreements | Other liabilities and accrued expenses | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount		28
Total liability derivatives, Fair value, net		(5)
Liability derivatives, Gross liability		(5)
Interest rate swap agreements | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	1,185	85
Total liability derivatives, Fair value, net	16	8
Liability derivatives, Gross asset	18	8
Liability derivatives, Gross liability	(2)
Foreign currency swap agreements | Other investments | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	16	127
Total asset derivatives, Fair value, net	2	(5)
Asset derivatives, Gross asset	2	3
Asset derivatives, Gross liability		(8)
Foreign currency swap agreements | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		50
Total asset derivatives, Fair value, net		6
Asset derivatives, Gross asset		6
Foreign currency swap agreements | Other liabilities and accrued expenses | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	135	50
Total liability derivatives, Fair value, net	(19)	(7)
Liability derivatives, Gross liability	(19)	(7)
Interest rate swaption agreements | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		1,750
Interest rate swaption agreements | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	250	1,250
Interest rate cap and floor agreements | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	372	1,591
Total asset derivatives, Fair value, net	1	(12)
Asset derivatives, Gross asset	1
Asset derivatives, Gross liability		(12)
Interest rate cap and floor agreements | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	429	914
Total liability derivatives, Fair value, net	1	(9)
Liability derivatives, Gross asset	1
Liability derivatives, Gross liability		(9)
Financial futures contracts and options | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Number of contracts	2	40
Financial futures contracts and options | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Number of contracts	357
Options, futures and warrants | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	146	163
Total asset derivatives, Number of contracts	12,400	15,180
Total asset derivatives, Fair value, net	125	104
Asset derivatives, Gross asset	125	104
Options, futures and warrants | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Number of contracts	1,087	2,132
Total asset derivatives, Fair value, net	5	1
Asset derivatives, Gross asset	5	1
Options, futures and warrants | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Number of contracts	12,262	15,677
Total liability derivatives, Fair value, net	(58)	(50)
Liability derivatives, Gross liability	(58)	(50)
Foreign currency forwards and options | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	258	190
Total asset derivatives, Fair value, net	6	1
Asset derivatives, Gross asset	6	3
Asset derivatives, Gross liability		(2)
Foreign currency forwards and options | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	139	96
Total liability derivatives, Fair value, net	(1)	(1)
Liability derivatives, Gross asset	1
Liability derivatives, Gross liability	(2)	(1)
Conversion options | Fixed income securities | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	5	5
Equity-indexed call options | Fixed income securities | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	90	150
Total asset derivatives, Fair value, net	9	11
Asset derivatives, Gross asset	9	11
Credit default swaps | Fixed income securities | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	12	172
Total asset derivatives, Fair value, net	(12)	(115)
Asset derivatives, Gross liability	(12)	(115)
Guaranteed accumulation benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	820	917
Total liability derivatives, Fair value, net	(86)	(105)
Liability derivatives, Gross liability	(86)	(105)
Guaranteed withdrawal benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	554	613
Total liability derivatives, Fair value, net	(39)	(57)
Liability derivatives, Gross liability	(39)	(57)
Equity-indexed and forward starting options in life and annuity product contracts | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	3,916	3,996
Total liability derivatives, Fair value, net	(419)	(553)
Liability derivatives, Gross liability	(419)	(553)
Other embedded derivative financial instruments | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	1,000	1,000
Other embedded derivative financial instruments | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	85	85
Total liability derivatives, Fair value, net	(9)	(8)
Liability derivatives, Gross liability	(9)	(8)
Credit Default Swaps - Buying Protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	209	265
Total asset derivatives, Fair value, net		3
Asset derivatives, Gross asset	2	6
Asset derivatives, Gross liability	(2)	(3)
Credit Default Swaps - Buying Protection | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	420	509
Total liability derivatives, Fair value, net	(3)	7
Liability derivatives, Gross asset	2	12
Liability derivatives, Gross liability	(5)	(5)
Credit Default Swaps - Selling Protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	308	167
Total asset derivatives, Fair value, net	2	(4)
Asset derivatives, Gross asset	3	1
Asset derivatives, Gross liability	(1)	(5)
Credit Default Swaps - Selling Protection | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	285	503
Total liability derivatives, Fair value, net	(29)	(77)
Liability derivatives, Gross asset	1	2
Liability derivatives, Gross liability	(30)	(79)
Other contracts | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		5
Other contracts | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	4	4
Total asset derivatives, Fair value, net	1	1
Asset derivatives, Gross asset	$ 1	$ 1