Derivative Financial Instruments (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 contract	Dec. 31, 2014 contract
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Assumed recoveries under sale of credit protection	$ 0
Cash and securities pledged in the form of margin deposits	41
Derivatives, Fair Value
Total asset derivatives, Notional amount	1,538	1,851
Total liability derivatives, Notional amount	(3,959)	(3,910)
Total derivatives, Notional amount	5,497	5,761
Total asset derivatives, Number of contracts	6,410	5,429
Total liability derivatives, Number of contracts	4,296	4,660
Total derivatives, Number of contracts	10,706	10,089
Derivative assets net amount on balance sheet	85	78
Asset derivatives, Gross asset	(87)	(94)
Asset derivatives, Gross liability	(2)	(16)
Derivative liabilities net amount on balance sheet	(383)	(361)
Total derivatives, Fair value, net	(298)	(283)
Liability derivatives, Gross asset	2	6
Liability derivatives, Gross liability	(385)	(367)
Number of stock rights and warrants held by the company related to derivative contracts (in shares)	220	220
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	1,454	1,766
Total liability derivatives, Notional amount	(3,959)	(3,860)
Total asset derivatives, Number of contracts	6,410	5,429
Total liability derivatives, Number of contracts	4,296	4,660
Derivative assets net amount on balance sheet	77	75
Asset derivatives, Gross asset	(78)	(91)
Asset derivatives, Gross liability	(1)	(16)
Derivative liabilities net amount on balance sheet	(383)	(360)
Liability derivatives, Gross asset	2	6
Liability derivatives, Gross liability	(385)	(366)
Interest rate swap agreements | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	(85)	(85)
Derivative liabilities net amount on balance sheet	0	1
Liability derivatives, Gross asset	0	1
Liability derivatives, Gross liability	0	0
Foreign currency swap agreements | Other investments | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	84	85
Derivative assets net amount on balance sheet	8	3
Asset derivatives, Gross asset	(9)	(3)
Asset derivatives, Gross liability	(1)	0
Foreign currency swap agreements | Other liabilities & accrued expenses | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount		(50)
Derivative liabilities net amount on balance sheet		(1)
Liability derivatives, Gross asset		0
Liability derivatives, Gross liability		(1)
Interest rate swaption agreements | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount		(11)
Derivative liabilities net amount on balance sheet		0
Liability derivatives, Gross asset		0
Liability derivatives, Gross liability		0
Interest rate cap agreements | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	153	163
Derivative assets net amount on balance sheet	1	2
Asset derivatives, Gross asset	(1)	(2)
Asset derivatives, Gross liability	0	0
Interest rate cap agreements | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	(12)
Derivative liabilities net amount on balance sheet	0
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	0
Financial futures contracts - Interest rate contracts | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	0	0
Total liability derivatives, Number of contracts	495	700
Derivative liabilities net amount on balance sheet	0	0
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	0	0
Options and futures | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	0	0
Total liability derivatives, Number of contracts	3,801	3,960
Derivative liabilities net amount on balance sheet	(11)	(23)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(11)	(23)
Options and warrants | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	0	0
Total asset derivatives, Number of contracts	3,070	3,225
Derivative assets net amount on balance sheet	69	83
Asset derivatives, Gross asset	(69)	(83)
Asset derivatives, Gross liability	0	0
Financial futures contracts - Equity and index contracts | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	0	0
Total asset derivatives, Number of contracts	3,340	2,204
Derivative assets net amount on balance sheet	1	2
Asset derivatives, Gross asset	(1)	(2)
Asset derivatives, Gross liability	0	0
Foreign currency forwards | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	78	471
Derivative assets net amount on balance sheet	2	(15)
Asset derivatives, Gross asset	(2)	(1)
Asset derivatives, Gross liability	0	(16)
Foreign currency forwards | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	(627)	(228)
Derivative liabilities net amount on balance sheet	(32)	(1)
Liability derivatives, Gross asset	2	2
Liability derivatives, Gross liability	(34)	(3)
Guaranteed accumulation benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	(590)	(615)
Derivative liabilities net amount on balance sheet	(31)	(32)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(31)	(32)
Guaranteed withdrawal benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	(408)	(425)
Derivative liabilities net amount on balance sheet	(14)	(13)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(14)	(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	(1,785)	(1,786)
Derivative liabilities net amount on balance sheet	(281)	(278)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(281)	(278)
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
Derivative assets net amount on balance sheet	0	0
Asset derivatives, Gross asset	0	0
Asset derivatives, Gross liability	0	0
Other embedded derivative financial instruments | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	(85)	(85)
Derivative liabilities net amount on balance sheet	0	0
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	0	0
Credit default swaps – buying protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	75	29
Derivative assets net amount on balance sheet	0	0
Asset derivatives, Gross asset	(1)	0
Asset derivatives, Gross liability	(1)	0
Credit default swaps – buying protection | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	(232)	(420)
Derivative liabilities net amount on balance sheet	(5)	(6)
Liability derivatives, Gross asset	0	1
Liability derivatives, Gross liability	(5)	(7)
Credit default swaps – selling protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	145	100
Derivative assets net amount on balance sheet	3	2
Asset derivatives, Gross asset	(3)	(2)
Asset derivatives, Gross liability	0	0
Credit default swaps – selling protection | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	(135)	(205)
Derivative liabilities net amount on balance sheet	(9)	(8)
Liability derivatives, Gross asset	0	2
Liability derivatives, Gross liability	(9)	(10)
Other contracts | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	3	3
Derivative assets net amount on balance sheet	1	1
Asset derivatives, Gross asset	(1)	(1)
Asset derivatives, Gross liability	$ 0	$ 0