Derivative Financial Instruments (Details) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2012 contract	Dec. 31, 2011 contract
Derivative Financial Instruments
Cash and securities pledged in the form of margin deposits	$ 9
Derivatives, Fair Value
Total asset derivatives, Notional amount	11,174	13,811
Total liability derivatives, Notional amount	6,714	9,046
Total derivatives, Notional amount	17,888	22,857
Total asset derivatives, Number of contracts	16,269	17,352
Total liability derivatives, Number of contracts	14,415	15,677
Total derivatives, Number of contracts	30,684	33,029
Asset derivatives, Gross asset	330	273
Asset derivatives, Gross liability	(43)	(168)
Total asset derivatives, Fair value, net	287	105
Liability derivatives, Gross asset	18	22
Liability derivatives, Gross liability	(703)	(879)
Total liability derivatives, Fair value, net	(685)	(857)
Total derivatives, Fair value, net	(398)	(752)
Number of stock rights held by the company related to derivative contracts (in shares)	7,307	10,798
Number of stock warrants held by the company related to derivative contracts (in shares)	3,915,485	4,392,937
Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	101	271
Total liability derivatives, Notional amount	50	78
Asset derivatives, Gross asset	2	3
Asset derivatives, Gross liability	(8)	(16)
Total asset derivatives, Fair value, net	(6)	(13)
Liability derivatives, Gross liability	(9)	(12)
Total liability derivatives, Fair value, net	(9)	(12)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	11,073	13,540
Total liability derivatives, Notional amount	6,664	8,968
Total asset derivatives, Number of contracts	16,269	17,352
Total liability derivatives, Number of contracts	14,415	15,677
Asset derivatives, Gross asset	328	270
Asset derivatives, Gross liability	(35)	(152)
Total asset derivatives, Fair value, net	293	118
Liability derivatives, Gross asset	18	22
Liability derivatives, Gross liability	(694)	(867)
Total liability derivatives, Fair value, net	(676)	(845)
Interest rate swap agreements | Other investments | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		144
Asset derivatives, Gross liability		(8)
Total asset derivatives, Fair value, net		(8)
Interest rate swap agreements | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	7,941	8,028
Asset derivatives, Gross asset	74	137
Asset derivatives, Gross liability	(18)	(15)
Total asset derivatives, Fair value, net	56	122
Interest rate swap agreements | Other liabilities and accrued expenses | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount		28
Liability derivatives, Gross liability		(5)
Total liability derivatives, Fair value, net		(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	85	85
Liability derivatives, Gross asset	9	8
Total liability derivatives, Fair value, net	9	8
Foreign currency swap agreements | Other investments | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	101	127
Asset derivatives, Gross asset	2	3
Asset derivatives, Gross liability	(8)	(8)
Total asset derivatives, Fair value, net	(6)	(5)
Foreign currency swap agreements | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		50
Asset derivatives, Gross asset		6
Total asset derivatives, Fair value, net		6
Foreign currency swap agreements | Other liabilities and accrued expenses | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	50	50
Liability derivatives, Gross liability	(9)	(7)
Total liability derivatives, Fair value, net	(9)	(7)
Interest rate swaption agreements | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	250	1,750
Interest rate swaption agreements | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		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	673	1,591
Asset derivatives, Gross asset	2
Asset derivatives, Gross liability		(12)
Total asset derivatives, Fair value, net	2	(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	359	914
Liability derivatives, Gross liability		(9)
Total liability derivatives, Fair value, net		(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	496
Options and futures | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	147	163
Total asset derivatives, Number of contracts	14,600	15,180
Asset derivatives, Gross asset	226	104
Total asset derivatives, Fair value, net	226	104
Options and futures | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Number of contracts	1,667	2,132
Asset derivatives, Gross asset	1	1
Total asset derivatives, Fair value, net	1	1
Options and futures | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Number of contracts	13,919	15,677
Liability derivatives, Gross liability	(106)	(50)
Total liability derivatives, Fair value, net	(106)	(50)
Foreign currency forwards and options | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	206	190
Asset derivatives, Gross asset	5	3
Asset derivatives, Gross liability	(1)	(2)
Total asset derivatives, Fair value, net	4	1
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	222	96
Liability derivatives, Gross asset	6
Liability derivatives, Gross liability		(1)
Total liability derivatives, Fair value, net	6	(1)
Conversion options | Fixed income securities | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	5	5
Asset derivatives, Gross asset	1
Total asset derivatives, Fair value, net	1
Equity-indexed call options | Fixed income securities | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	90	150
Asset derivatives, Gross asset	10	11
Total asset derivatives, Fair value, net	10	11
Credit default swaps | Fixed income securities | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	12	172
Asset derivatives, Gross liability	(12)	(115)
Total asset derivatives, Fair value, net	(12)	(115)
Guaranteed accumulation benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	853	917
Liability derivatives, Gross liability	(85)	(105)
Total liability derivatives, Fair value, net	(85)	(105)
Guaranteed withdrawal benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	573	613
Liability derivatives, Gross liability	(44)	(57)
Total liability derivatives, Fair value, net	(44)	(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	3,835	3,996
Liability derivatives, Gross liability	(413)	(553)
Total liability derivatives, Fair value, net	(413)	(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
Liability derivatives, Gross liability	(9)	(8)
Total liability derivatives, Fair value, net	(9)	(8)
Credit Default Swaps - Buying Protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	470	265
Asset derivatives, Gross asset	6	6
Asset derivatives, Gross liability	(4)	(3)
Total asset derivatives, Fair value, net	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	314	509
Liability derivatives, Gross asset	2	12
Liability derivatives, Gross liability	(3)	(5)
Total liability derivatives, Fair value, net	(1)	7
Credit Default Swaps - Selling Protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	275	167
Asset derivatives, Gross asset	2	1
Asset derivatives, Gross liability		(5)
Total asset derivatives, Fair value, net	2	(4)
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	338	503
Liability derivatives, Gross asset	1	2
Liability derivatives, Gross liability	(34)	(79)
Total liability derivatives, Fair value, net	(33)	(77)
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
Asset derivatives, Gross asset	1	1
Total asset derivatives, Fair value, net	$ 1	$ 1