Derivative Financial Instruments and Off-balance sheet Financial Instruments (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014 contract	Dec. 31, 2013 contract
Derivative Financial Instruments and Off-balance sheet Financial Instruments
Assumed recoveries under sale of credit protection	$ 0
Cash and securities pledged in the form of margin deposits	41us-gaap_MarginDepositAssets
Derivatives, Fair Value
Total asset derivatives, Notional amount	1,851us-gaap_DerivativeAssetNotionalAmount	2,784us-gaap_DerivativeAssetNotionalAmount
Total liability derivatives, Notional amount	3,910	11,219
Total derivatives, Notional amount	5,761invest_DerivativeNotionalAmount	14,003invest_DerivativeNotionalAmount
Total asset derivatives, Number of contracts	5,429	12,017
Total liability derivatives, Number of contracts	4,660	10,035
Total derivatives, Number of contracts	10,089	22,052
Derivative assets net amount on balance sheet	78us-gaap_DerivativeAssets	267us-gaap_DerivativeAssets
Asset derivatives, Gross asset	94	279
Asset derivatives, Gross liability	(16)	(12)
Total liability derivatives, Fair value, net	(361)us-gaap_DerivativeLiabilities	(746)us-gaap_DerivativeLiabilities
Total derivatives, Fair value, net	(283)	(479)
Liability derivatives, Gross asset	6	15
Liability derivatives, Gross liability	(367)	(761)
Number of stock rights and warrants held by the company related to derivative contracts (in shares)	220	1,238,580
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	1,766	2,768
Total liability derivatives, Notional amount	3,860	11,087
Total asset derivatives, Number of contracts	5,429	12,017
Total liability derivatives, Number of contracts	4,660	10,035
Derivative assets net amount on balance sheet	75	266
Asset derivatives, Gross asset	91	278
Asset derivatives, Gross liability	(16)	(12)
Total liability derivatives, Fair value, net	(360)	(731)
Liability derivatives, Gross asset	6	15
Liability derivatives, Gross liability	(366)	(746)
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
Total liability derivatives, Fair value, net	1	4
Liability derivatives, Gross asset	1	4
Foreign currency swap agreements \| Other investments \| Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	85	16
Derivative assets net amount on balance sheet	3	1
Asset derivatives, Gross asset	3	1
Foreign currency swap agreements \| Other liabilities and accrued expenses \| Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	50	132
Total liability derivatives, Fair value, net	(1)	(15)
Liability derivatives, Gross liability	(1)	(15)
Interest rate swaption agreements \| Other investments \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		1,420
Interest rate swaption agreements \| Other liabilities and accrued expenses \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount		4,570
Total liability derivatives, Fair value, net		1
Liability derivatives, Gross asset		1
Interest rate cap agreements \| Other investments \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	163	61
Derivative assets net amount on balance sheet	2	2
Asset derivatives, Gross asset	2	2
Interest rate cap agreements \| Other liabilities and accrued expenses \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	11	262
Total liability derivatives, Fair value, net		4
Liability derivatives, Gross asset		4
Financial futures contracts - Interest rate contracts \| Other assets \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Number of contracts		550
Financial futures contracts - Interest rate contracts \| Other liabilities and accrued expenses \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Number of contracts	700
Options \| Other liabilities and accrued expenses \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount		55
Total liability derivatives, Number of contracts		10,035
Total liability derivatives, Fair value, net		(165)
Liability derivatives, Gross asset		2
Liability derivatives, Gross liability		(167)
Options and futures \| Other liabilities and accrued expenses \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Number of contracts	3,960
Total liability derivatives, Fair value, net	(23)
Liability derivatives, Gross liability	(23)
Options and warrants \| Other investments \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		3
Total asset derivatives, Number of contracts	3,225	10,035
Derivative assets net amount on balance sheet	83	263
Asset derivatives, Gross asset	83	263
Financial futures contracts - Equity and index contracts \| Other assets \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Number of contracts	2,204	1,432
Derivative assets net amount on balance sheet	2	1
Asset derivatives, Gross asset	2	1
Foreign currency forwards \| Other investments \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	471	161
Derivative assets net amount on balance sheet	(15)	10
Asset derivatives, Gross asset	1	10
Asset derivatives, Gross liability	(16)
Foreign currency forwards \| Other liabilities and accrued expenses \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	228	148
Total liability derivatives, Fair value, net	(1)	(3)
Liability derivatives, Gross asset	2	2
Liability derivatives, Gross liability	(3)	(5)
Credit default swaps
Derivatives, Fair Value
Total derivatives, Notional amount	305	290
Credit default swaps \| Fixed income securities \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		12
Derivative assets net amount on balance sheet		(12)
Asset derivatives, Gross liability		(12)
Guaranteed accumulation benefits \| Contractholder funds \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	615	738
Total liability derivatives, Fair value, net	(32)	(43)
Liability derivatives, Gross liability	(32)	(43)
Guaranteed withdrawal benefits \| Contractholder funds \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	425	506
Total liability derivatives, Fair value, net	(13)	(13)
Liability derivatives, Gross liability	(13)	(13)
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	1,786	1,693
Total liability derivatives, Fair value, net	(278)	(247)
Liability derivatives, Gross liability	(278)	(247)
Equity-indexed and forward starting options in life and annuity product contracts \| Liabilities held for sale \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount		2,363
Total liability derivatives, Fair value, net		(246)
Liability derivatives, Gross liability		(246)
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		(4)
Liability derivatives, Gross liability		(4)
Credit Default Swaps - Buying Protection \| Other investments \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	29	2
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	397
Total liability derivatives, Fair value, net	(6)	(6)
Liability derivatives, Gross asset	1
Liability derivatives, Gross liability	(7)	(6)
Credit Default Swaps - Selling Protection \| Other investments \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	100	105
Derivative assets net amount on balance sheet	2	2
Asset derivatives, Gross asset	2	2
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	205	185
Total liability derivatives, Fair value, net	(8)	(13)
Liability derivatives, Gross asset	2	2
Liability derivatives, Gross liability	(10)	(15)
Other contracts \| Other assets \| Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	3	4
Derivative assets net amount on balance sheet	1
Asset derivatives, Gross asset	$ 1

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The number of stock rights and warrants held by the company as of the balance sheet date which are related to derivative contracts.

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Represents the potential amount of recoveries under sale of credit protection.

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Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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Nominal or face amount used to calculate payments on the derivative asset.

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The number of derivative instruments of a particular derivative asset or group of derivative assets held by the entity.

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value of asset associated with financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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Nominal or face amount used to calculate payments on the derivative liability.

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The number of derivative instruments of a particular derivative liability or group of derivative liabilities held by the entity.

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The number of derivative instruments of a particular group held by the entity.

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The amount of cash or securities placed with a broker or counterparty as security for a trading or derivatives securities position which was partially obtained with funds provided by the broker dealer.

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