Derivative Financial Instruments (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 contract	Dec. 31, 2012 contract
Derivative Financial Instruments
Assumed recoveries under sale of credit protection	$ 0
Securities pledged in the form of margin deposits	4,000,000
Derivatives, Fair Value
Total asset derivatives, Notional amount	4,676,000,000	6,362,000,000
Total liability derivatives, Notional amount	9,034,000,000	7,697,000,000
Total derivatives, Notional amount	13,710,000,000	14,059,000,000
Total asset derivatives, Number of contracts	12,559	12,651
Total liability derivatives, Number of contracts	11,539	12,619
Total derivatives, Number of contracts	24,098	25,270
Total asset derivatives, Fair value, net	224,000,000	147,000,000
Asset derivatives, Gross asset	244,000,000	169,000,000
Asset derivatives, Gross liability	(20,000,000)	(22,000,000)
Total liability derivatives, Fair value, net	(713,000,000)	(645,000,000)
Total derivatives, Fair value, net	(489,000,000)	(498,000,000)
Liability derivatives, Gross asset	25,000,000	19,000,000
Liability derivatives, Gross liability	(738,000,000)	(664,000,000)
Number of stock warrants held by the company related to derivative contracts	837,100	837,100
Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	16,000,000	16,000,000
Total liability derivatives, Notional amount	132,000,000	135,000,000
Total asset derivatives, Fair value, net	3,000,000	2,000,000
Asset derivatives, Gross asset	3,000,000	2,000,000
Total liability derivatives, Fair value, net	(17,000,000)	(19,000,000)
Liability derivatives, Gross liability	(17,000,000)	(19,000,000)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	4,660,000,000	6,346,000,000
Total liability derivatives, Notional amount	8,902,000,000	7,562,000,000
Total asset derivatives, Number of contracts	12,559	12,651
Total liability derivatives, Number of contracts	11,539	12,619
Total asset derivatives, Fair value, net	221,000,000	145,000,000
Asset derivatives, Gross asset	241,000,000	167,000,000
Asset derivatives, Gross liability	(20,000,000)	(22,000,000)
Total liability derivatives, Fair value, net	(696,000,000)	(626,000,000)
Liability derivatives, Gross asset	25,000,000	19,000,000
Liability derivatives, Gross liability	(721,000,000)	(645,000,000)
Interest rate swap agreements | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	4,284,000,000	5,541,000,000
Total asset derivatives, Fair value, net	18,000,000	19,000,000
Asset derivatives, Gross asset	26,000,000	28,000,000
Asset derivatives, Gross liability	(8,000,000)	(9,000,000)
Interest rate swap agreements | Derivatives not designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	2,185,000,000	1,185,000,000
Total liability derivatives, Fair value, net	20,000,000	16,000,000
Liability derivatives, Gross asset	22,000,000	18,000,000
Liability derivatives, Gross liability	(2,000,000)	(2,000,000)
Other contracts | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount	4,000,000	4,000,000
Total asset derivatives, Fair value, net	1,000,000	1,000,000
Asset derivatives, Gross asset	1,000,000	1,000,000
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	16,000,000	16,000,000
Total asset derivatives, Fair value, net	3,000,000	2,000,000
Asset derivatives, Gross asset	3,000,000	2,000,000
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	132,000,000	135,000,000
Total liability derivatives, Fair value, net	(17,000,000)	(19,000,000)
Liability derivatives, Gross liability	(17,000,000)	(19,000,000)
Interest rate swaption agreements | Derivatives not designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	250,000,000	250,000,000
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	159,000,000	372,000,000
Total asset derivatives, Fair value, net	1,000,000	1,000,000
Asset derivatives, Gross asset	1,000,000	1,000,000
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	380,000,000	429,000,000
Total liability derivatives, Fair value, net	2,000,000	1,000,000
Liability derivatives, Gross asset	2,000,000	1,000,000
Financial futures contracts and options | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Number of contracts	238	2
Financial futures contracts and options | Derivatives not designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Number of contracts		357
Options and warrants | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	10,000,000	146,000,000
Total asset derivatives, Number of contracts	12,230	12,400
Total asset derivatives, Fair value, net	212,000,000	125,000,000
Asset derivatives, Gross asset	212,000,000	125,000,000
Options and warrants | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Number of contracts		249
Total asset derivatives, Fair value, net		2,000,000
Asset derivatives, Gross asset		2,000,000
Options and futures | Derivatives not designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	125,000,000
Total liability derivatives, Number of contracts	11,539	12,262
Total liability derivatives, Fair value, net	(125,000,000)	(58,000,000)
Liability derivatives, Gross asset	1,000,000
Liability derivatives, Gross liability	(126,000,000)	(58,000,000)
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	44,000,000	44,000,000
Conversion options | Derivatives not designated as accounting hedging instruments | Fixed income securities
Derivatives, Fair Value
Total asset derivatives, Notional amount	5,000,000	5,000,000
Equity-indexed call options | Derivatives not designated as accounting hedging instruments | Fixed income securities
Derivatives, Fair Value
Total asset derivatives, Notional amount		90,000,000
Total asset derivatives, Fair value, net		9,000,000
Asset derivatives, Gross asset		9,000,000
Credit default swaps | Derivatives not designated as accounting hedging instruments | Fixed income securities
Derivatives, Fair Value
Total asset derivatives, Notional amount	12,000,000	12,000,000
Total asset derivatives, Fair value, net	(12,000,000)	(12,000,000)
Asset derivatives, Gross liability	(12,000,000)	(12,000,000)
Guaranteed accumulation benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	939,000,000	820,000,000
Total liability derivatives, Fair value, net	(70,000,000)	(86,000,000)
Liability derivatives, Gross liability	(70,000,000)	(86,000,000)
Guaranteed withdrawal benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	635,000,000	554,000,000
Total liability derivatives, Fair value, net	(30,000,000)	(39,000,000)
Liability derivatives, Gross liability	(30,000,000)	(39,000,000)
Equity-indexed and forward starting options in life and annuity product contracts | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	3,998,000,000	3,916,000,000
Total liability derivatives, Fair value, net	(459,000,000)	(419,000,000)
Liability derivatives, Gross liability	(459,000,000)	(419,000,000)
Other embedded derivative financial instruments | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	85,000,000	85,000,000
Total liability derivatives, Fair value, net	(8,000,000)	(9,000,000)
Liability derivatives, Gross liability	(8,000,000)	(9,000,000)
Credit default swaps - buying protection | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	37,000,000	32,000,000
Total asset derivatives, Fair value, net		(1,000,000)
Asset derivatives, Gross liability		(1,000,000)
Credit default swaps - buying protection | Derivatives not designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	180,000,000	193,000,000
Total liability derivatives, Fair value, net	(2,000,000)	(2,000,000)
Liability derivatives, Gross liability	(2,000,000)	(2,000,000)
Credit default swaps - selling protection | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	105,000,000	100,000,000
Total asset derivatives, Fair value, net	1,000,000	1,000,000
Asset derivatives, Gross asset	1,000,000	1,000,000
Credit default swaps - selling protection | Derivatives not designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	125,000,000	130,000,000
Total liability derivatives, Fair value, net	(24,000,000)	(30,000,000)
Liability derivatives, Gross liability	$ (24,000,000)	$ (30,000,000)
Options, futures and warrants | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total liability derivatives, Number of contracts	91