Derivative Financial Instruments (Details) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2012 contract	Dec. 31, 2011 contract
Derivative Financial Instruments
Cash and securities pledged in the form of margin deposits	$ 10
Derivatives, Fair Value
Total asset derivatives, Notional amount	9,736	13,811
Total liability derivatives, Notional amount	8,978	9,046
Total derivatives, Notional amount	18,714	22,857
Total asset derivatives, Number of contracts	14,927	17,352
Total liability derivatives, Number of contracts	16,675	15,677
Total derivatives, Number of contracts	31,602	33,029
Asset derivatives, Gross asset	259	273
Asset derivatives, Gross liability	(90)	(168)
Total asset derivatives, Fair value, net	169	105
Liability derivatives, Gross asset	30	22
Liability derivatives, Gross liability	(874)	(879)
Total liability derivatives, Fair value, net	(844)	(857)
Total derivatives, Fair value, net	(675)	(752)
Number of stock rights held by the company related to derivative contracts (in shares)	24,160	10,798
Number of stock warrants held by the company related to derivative contracts (in shares)	3,925,327	4,392,937
Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	112	271
Total liability derivatives, Notional amount	66	78
Asset derivatives, Gross asset		3
Asset derivatives, Gross liability	(6)	(16)
Total asset derivatives, Fair value, net	(6)	(13)
Liability derivatives, Gross asset	2
Liability derivatives, Gross liability	(7)	(12)
Total liability derivatives, Fair value, net	(5)	(12)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	9,624	13,540
Total liability derivatives, Notional amount	8,912	8,968
Total asset derivatives, Number of contracts	14,927	17,352
Total liability derivatives, Number of contracts	16,675	15,677
Asset derivatives, Gross asset	259	270
Asset derivatives, Gross liability	(84)	(152)
Total asset derivatives, Fair value, net	175	118
Liability derivatives, Gross asset	28	22
Liability derivatives, Gross liability	(867)	(867)
Total liability derivatives, Fair value, net	(839)	(845)
Interest rate swap agreements | Other investments | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	27	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	6,941	8,028
Asset derivatives, Gross asset	57	137
Asset derivatives, Gross liability	(12)	(15)
Total asset derivatives, Fair value, net	45	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	1,135	85
Liability derivatives, Gross asset	17	8
Liability derivatives, Gross liability	(3)
Total liability derivatives, Fair value, net	14	8
Foreign currency swap agreements | Other investments | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	85	127
Asset derivatives, Gross asset		3
Asset derivatives, Gross liability	(6)	(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	66	50
Liability derivatives, Gross asset	2
Liability derivatives, Gross liability	(7)	(7)
Total liability derivatives, Fair value, net	(5)	(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 liability 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	449	1,591
Asset derivatives, Gross asset	1
Asset derivatives, Gross liability	(12)	(12)
Total asset derivatives, Fair value, net	(11)	(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	841	914
Liability derivatives, Gross liability	(7)	(9)
Total liability derivatives, Fair value, net	(7)	(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	630
Options and futures | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	150	163
Total asset derivatives, Number of contracts	13,740	15,180
Asset derivatives, Gross asset	171	104
Total asset derivatives, Fair value, net	171	104
Options and futures | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Number of contracts	1,185	2,132
Asset derivatives, Gross asset	6	1
Total asset derivatives, Fair value, net	6	1
Options and futures | Other liabilities and accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	2
Total liability derivatives, Number of contracts	16,045	15,677
Liability derivatives, Gross liability	(81)	(50)
Total liability derivatives, Fair value, net	(81)	(50)
Foreign currency forwards and options | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	134	190
Asset derivatives, Gross asset	2	3
Asset derivatives, Gross liability		(2)
Total asset derivatives, Fair value, net	2	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	324	96
Liability derivatives, Gross asset	1
Liability derivatives, Gross liability	(6)	(1)
Total liability derivatives, Fair value, net	(5)	(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	125	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	129	172
Asset derivatives, Gross liability	(56)	(115)
Total asset derivatives, Fair value, net	(56)	(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	(96)	(105)
Total liability derivatives, Fair value, net	(96)	(105)
Guaranteed withdrawal benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	571	613
Liability derivatives, Gross liability	(52)	(57)
Total liability derivatives, Fair value, net	(52)	(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	3,756	3,996
Liability derivatives, Gross liability	(551)	(553)
Total liability derivatives, Fair value, net	(551)	(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	(8)	(8)
Total liability derivatives, Fair value, net	(8)	(8)
Credit Default Swaps - Buying Protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	257	265
Asset derivatives, Gross asset	8	6
Asset derivatives, Gross liability	(3)	(3)
Total asset derivatives, Fair value, net	5	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	712	509
Liability derivatives, Gross asset	10	12
Liability derivatives, Gross liability	(3)	(5)
Total liability derivatives, Fair value, net	7	7
Credit Default Swaps - Selling Protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	180	167
Asset derivatives, Gross asset	3	1
Asset derivatives, Gross liability	(1)	(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	633	503
Liability derivatives, Gross asset		2
Liability derivatives, Gross liability	(60)	(79)
Total liability derivatives, Fair value, net	(60)	(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