Derivative Financial Instruments (Details) (USD $)	6 Months Ended
	Jun. 30, 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	1,946,000,000	6,362,000,000
Total liability derivatives, Notional amount	6,052,000,000	7,697,000,000
Total derivatives, Notional amount	7,998,000,000	14,059,000,000
Total asset derivatives, Number of contracts	11,110	12,651
Total liability derivatives, Number of contracts	11,260	12,619
Total derivatives, Number of contracts	22,370	25,270
Total asset derivatives, Fair value, net	191,000,000	147,000,000
Asset derivatives, Gross asset	209,000,000	169,000,000
Asset derivatives, Gross liability	(18,000,000)	(22,000,000)
Total liability derivatives, Fair value, net	(664,000,000)	(645,000,000)
Total derivatives, Fair value, net	(473,000,000)	(498,000,000)
Liability derivatives, Gross asset	5,000,000	19,000,000
Liability derivatives, Gross liability	(669,000,000)	(664,000,000)
Number of stock warrants held by the company related to derivative contracts (in shares)	837,100	837,100
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	1,857,000,000	6,346,000,000
Total liability derivatives, Notional amount	5,993,000,000	7,562,000,000
Total asset derivatives, Number of contracts	11,110	12,651
Total liability derivatives, Number of contracts	11,260	12,619
Total asset derivatives, Fair value, net	192,000,000	145,000,000
Asset derivatives, Gross asset	206,000,000	167,000,000
Asset derivatives, Gross liability	(14,000,000)	(22,000,000)
Total liability derivatives, Fair value, net	(659,000,000)	(626,000,000)
Liability derivatives, Gross asset	5,000,000	19,000,000
Liability derivatives, Gross liability	(664,000,000)	(645,000,000)
Interest rate swap agreements | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	1,332,000,000	5,541,000,000
Total asset derivatives, Fair value, net	6,000,000	19,000,000
Asset derivatives, Gross asset	7,000,000	28,000,000
Asset derivatives, Gross liability	(1,000,000)	(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	85,000,000	1,185,000,000
Total liability derivatives, Fair value, net	5,000,000	16,000,000
Liability derivatives, Gross asset	5,000,000	18,000,000
Liability derivatives, Gross liability		(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	89,000,000	16,000,000
Total asset derivatives, Fair value, net	(1,000,000)	2,000,000
Asset derivatives, Gross asset	3,000,000	2,000,000
Asset derivatives, Gross liability	(4,000,000)
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	59,000,000	135,000,000
Total liability derivatives, Fair value, net	(5,000,000)	(19,000,000)
Liability derivatives, Gross liability	(5,000,000)	(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
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	290,000,000	372,000,000
Total asset derivatives, Fair value, net	5,000,000	1,000,000
Asset derivatives, Gross asset	5,000,000	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	149,000,000	429,000,000
Total liability derivatives, Fair value, net		1,000,000
Liability derivatives, Gross asset		1,000,000
Financial futures contracts - Interest rate contracts | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Number of contracts		2
Financial futures contracts - Interest rate contracts | Derivatives not designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Number of contracts		357
Financial futures contracts - Equity and index contracts | 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 warrants | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	13,000,000	146,000,000
Total asset derivatives, Number of contracts	11,110	12,400
Total asset derivatives, Fair value, net	192,000,000	125,000,000
Asset derivatives, Gross asset	192,000,000	125,000,000
Options and futures | Derivatives not designated as accounting hedging instruments | Other liabilities and accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	108,000,000
Total liability derivatives, Number of contracts	11,260	12,262
Total liability derivatives, Fair value, net	(116,000,000)	(58,000,000)
Liability derivatives, Gross liability	(116,000,000)	(58,000,000)
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	45,000,000	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	786,000,000	820,000,000
Total liability derivatives, Fair value, net	(59,000,000)	(86,000,000)
Liability derivatives, Gross liability	(59,000,000)	(86,000,000)
Guaranteed withdrawal benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	539,000,000	554,000,000
Total liability derivatives, Fair value, net	(24,000,000)	(39,000,000)
Liability derivatives, Gross liability	(24,000,000)	(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	3,996,000,000	3,916,000,000
Total liability derivatives, Fair value, net	(445,000,000)	(419,000,000)
Liability derivatives, Gross liability	(445,000,000)	(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	(5,000,000)	(9,000,000)
Liability derivatives, Gross liability	(5,000,000)	(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	71,000,000	32,000,000
Total asset derivatives, Fair value, net	(1,000,000)	(1,000,000)
Asset derivatives, Gross liability	(1,000,000)	(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	145,000,000	193,000,000
Total liability derivatives, Fair value, net	(1,000,000)	(2,000,000)
Liability derivatives, Gross liability	(1,000,000)	(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	85,000,000	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	100,000,000	130,000,000
Total liability derivatives, Fair value, net	(14,000,000)	(30,000,000)
Liability derivatives, Gross liability	$ (14,000,000)	$ (30,000,000)