Derivative Financial Instruments (Details)	6 Months Ended
	Jun. 30, 2016 USD ($) contract	Dec. 31, 2015 USD ($) contract shares
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	14,000,000
Derivatives, Fair Value
Total asset derivatives, Notional amount	566,000,000	$ 1,568,000,000
Total liability derivatives, Notional amount	3,574,000,000	3,409,000,000
Total derivatives, Notional amount	$ 4,140,000,000	$ 4,977,000,000
Total asset derivatives, Number of contracts | contract	4,913	5,627
Total liability derivatives, Number of contracts | contract	6,350	4,406
Total derivatives, Number of contracts | contract	11,263	10,033
Derivative assets net amount on balance sheet	$ 55,000,000	$ 61,000,000
Asset derivatives gross amount	80,000,000	63,000,000
Asset derivatives, gross liability	(25,000,000)	(2,000,000)
Derivative liabilities net amount on balance sheet	(333,000,000)	(323,000,000)
Total derivatives, Fair value, net	(278,000,000)	(262,000,000)
Liability derivatives, gross asset	12,000,000	6,000,000
Liability derivatives, Gross liability	(345,000,000)	$ (329,000,000)
Number of stock rights and warrants held by the company related to derivative contracts (in shares) | shares		220
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	536,000,000	$ 1,523,000,000
Total liability derivatives, Notional amount	$ 3,555,000,000	$ 3,390,000,000
Total asset derivatives, Number of contracts | contract	4,913	5,627
Total liability derivatives, Number of contracts | contract	6,350	4,406
Derivative assets net amount on balance sheet	$ 53,000,000	$ 55,000,000
Asset derivatives gross amount	78,000,000	57,000,000
Asset derivatives, gross liability	(25,000,000)	(2,000,000)
Derivative liabilities net amount on balance sheet	(336,000,000)	(327,000,000)
Liability derivatives, gross asset	9,000,000	2,000,000
Liability derivatives, Gross liability	(345,000,000)	(329,000,000)
Interest rate swap agreements | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	85,000,000	85,000,000
Derivative liabilities net amount on balance sheet	0	0
Liability derivatives, gross asset	0	0
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	30,000,000	45,000,000
Derivative assets net amount on balance sheet	2,000,000	6,000,000
Asset derivatives gross amount	2,000,000	6,000,000
Asset derivatives, gross liability	0	0
Foreign currency swap agreements | Other liabilities & accrued expenses | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	19,000,000	19,000,000
Derivative liabilities net amount on balance sheet	3,000,000	4,000,000
Liability derivatives, gross asset	3,000,000	4,000,000
Liability derivatives, Gross liability	0	0
Interest rate cap agreements | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	24,000,000	42,000,000
Derivative assets net amount on balance sheet	0	0
Asset derivatives gross amount	0	0
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	51,000,000	72,000,000
Derivative liabilities net amount on balance sheet	1,000,000	1,000,000
Liability derivatives, gross asset	1,000,000	1,000,000
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 | contract	6,350	4,406
Derivative liabilities net amount on balance sheet	$ (21,000,000)	$ (7,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives, Gross liability	(21,000,000)	(7,000,000)
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 | contract	4,106	3,730
Derivative assets net amount on balance sheet	$ 66,000,000	$ 44,000,000
Asset derivatives gross amount	66,000,000	44,000,000
Asset derivatives, gross liability	0	0
Financial futures 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 | contract	807	1,897
Derivative assets net amount on balance sheet	$ 2,000,000	$ 2,000,000
Asset derivatives gross amount	2,000,000	2,000,000
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	399,000,000	185,000,000
Derivative assets net amount on balance sheet	(17,000,000)	1,000,000
Asset derivatives gross amount	8,000,000	2,000,000
Asset derivatives, gross liability	(25,000,000)	(1,000,000)
Foreign currency forwards | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	434,000,000	361,000,000
Derivative liabilities net amount on balance sheet	(1,000,000)	(12,000,000)
Liability derivatives, gross asset	7,000,000	1,000,000
Liability derivatives, Gross liability	(8,000,000)	(13,000,000)
Guaranteed accumulation benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	429,000,000	481,000,000
Derivative liabilities net amount on balance sheet	(40,000,000)	(38,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives, Gross liability	(40,000,000)	(38,000,000)
Guaranteed withdrawal benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	304,000,000	332,000,000
Derivative liabilities net amount on balance sheet	(14,000,000)	(14,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives, Gross liability	(14,000,000)	(14,000,000)
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	1,754,000,000	1,781,000,000
Derivative liabilities net amount on balance sheet	(250,000,000)	(247,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives, Gross liability	(250,000,000)	(247,000,000)
Other embedded derivative financial instruments | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		1,000,000,000
Derivative assets net amount on balance sheet		0
Asset derivatives gross amount		0
Asset derivatives, gross liability		0
Other embedded derivative financial instruments | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	85,000,000	85,000,000
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	30,000,000	112,000,000
Derivative assets net amount on balance sheet	0	4,000,000
Asset derivatives gross amount	0	5,000,000
Asset derivatives, gross liability	0	(1,000,000)
Credit default swaps – buying protection | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	248,000,000	88,000,000
Derivative liabilities net amount on balance sheet	(4,000,000)	(2,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives, Gross liability	(4,000,000)	(2,000,000)
Credit default swaps – selling protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	80,000,000	150,000,000
Derivative assets net amount on balance sheet	1,000,000	2,000,000
Asset derivatives gross amount	1,000,000	2,000,000
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	165,000,000	105,000,000
Derivative liabilities net amount on balance sheet	(7,000,000)	(8,000,000)
Liability derivatives, gross asset	1,000,000	0
Liability derivatives, Gross liability	(8,000,000)	(8,000,000)
Other contracts | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		31,000,000
Derivative assets net amount on balance sheet		1,000,000
Asset derivatives gross amount		1,000,000
Asset derivatives, gross liability		0
Other contracts | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	3,000,000	3,000,000
Derivative assets net amount on balance sheet	1,000,000	1,000,000
Asset derivatives gross amount	1,000,000	1,000,000
Asset derivatives, gross liability	$ 0	$ 0