Derivative Financial Instruments (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) contract shares	Dec. 31, 2015 USD ($) 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	12
Derivatives, Fair Value
Total asset derivatives, Notional amount	1,625	$ 1,568
Total liability derivatives, Notional amount	3,350	3,409
Total derivatives, Notional amount	$ 4,975	$ 4,977
Total asset derivatives, Number of contracts | contract	5,928	5,627
Total liability derivatives, Number of contracts | contract	4,045	4,406
Total derivatives, Number of contracts | contract	9,973	10,033
Derivative assets net amount on balance sheet	$ 53	$ 61
Asset derivatives gross amount	65	63
Asset derivatives, Gross liability	(12)	(2)
Derivative liabilities net amount on balance sheet	(337)	(323)
Total derivatives, Fair value, net	(284)	(262)
Liability derivatives, Gross asset	9	6
Liability derivatives, Gross liability	$ (346)	$ (329)
Number of stock rights and warrants held by the company related to derivative contracts (in shares) | shares	220	220
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 1,610	$ 1,523
Total liability derivatives, Notional amount	$ 3,301	$ 3,390
Total asset derivatives, Number of contracts | contract	5,928	5,627
Total liability derivatives, Number of contracts | contract	4,045	4,406
Derivative assets net amount on balance sheet	$ 50	$ 55
Asset derivatives gross amount	62	57
Asset derivatives, Gross liability	(12)	(2)
Derivative liabilities net amount on balance sheet	(341)	(327)
Liability derivatives, Gross asset	5	2
Liability derivatives, Gross liability	(346)	(329)
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	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	15	45
Derivative assets net amount on balance sheet	3	6
Asset derivatives gross amount	3	6
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	49	19
Derivative liabilities net amount on balance sheet	4	4
Liability derivatives, Gross asset	4	4
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	42
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	66	72
Derivative liabilities net amount on balance sheet	1	1
Liability derivatives, Gross asset	1	1
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	4,045	4,406
Derivative liabilities net amount on balance sheet	$ (11)	$ (7)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(11)	(7)
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	3,771	3,730
Derivative assets net amount on balance sheet	$ 51	$ 44
Asset derivatives gross amount	51	44
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 | contract	2,157	1,897
Derivative assets net amount on balance sheet	$ 0	$ 2
Asset derivatives gross amount	0	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	391	185
Derivative assets net amount on balance sheet	(3)	1
Asset derivatives gross amount	8	2
Asset derivatives, Gross liability	(11)	(1)
Foreign currency forwards | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	240	361
Derivative liabilities net amount on balance sheet	(7)	(12)
Liability derivatives, Gross asset	2	1
Liability derivatives, Gross liability	(9)	(13)
Guaranteed accumulation benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	423	481
Derivative liabilities net amount on balance sheet	(49)	(38)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(49)	(38)
Guaranteed withdrawal benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	292	332
Derivative liabilities net amount on balance sheet	(19)	(14)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(19)	(14)
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	1,769	1,781
Derivative liabilities net amount on balance sheet	(245)	(247)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(245)	(247)
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 amount	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	97	112
Derivative assets net amount on balance sheet	0	4
Asset derivatives gross amount	1	5
Asset derivatives, Gross liability	(1)	(1)
Credit default swaps – buying protection | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, Notional amount	181	88
Derivative liabilities net amount on balance sheet	(3)	(2)
Liability derivatives, Gross asset	1	0
Liability derivatives, Gross liability	(4)	(2)
Credit default swaps – selling protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	95	150
Derivative assets net amount on balance sheet	1	2
Asset derivatives gross amount	1	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	160	105
Derivative liabilities net amount on balance sheet	(8)	(8)
Liability derivatives, Gross asset	1	0
Liability derivatives, Gross liability	(9)	(8)
Other contracts | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount		31
Derivative assets net amount on balance sheet		1
Asset derivatives gross amount		1
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	3
Derivative assets net amount on balance sheet	1	1
Asset derivatives gross amount	1	1
Asset derivatives, Gross liability	$ 0	$ 0