Derivative Financial Instruments and Off-balance sheet Financial Instruments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) contract	Dec. 31, 2014 USD ($) contract
Derivative Financial Instruments and Off-balance sheet Financial Instruments
Assumed recoveries under sale of credit protection	$ 0
Securities pledged in the form of margin deposits	12
Derivatives, Fair Value
Total asset derivatives, Notional amount	302	$ 407
Total liability derivatives, Notional amount	2,957	3,242
Total derivatives, Notional amount	$ 3,259	$ 3,649
Total asset derivatives, Number of contracts | contract	4,727	3,929
Total liability derivatives, Number of contracts | contract	3,645	3,331
Total derivatives, Number of contracts | contract	8,372	7,260
Total asset derivatives, Fair value, net	$ 56	$ 92
Asset derivatives, Gross asset	57	92
Asset derivatives, Gross liability	(1)	0
Derivative liabilities net amount on balance sheet	(308)	(354)
Total derivatives, Fair value, net	(252)	(262)
Liability derivatives, Gross asset	5	2
Liability derivatives, Gross liability	(313)	(356)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	257	322
Total liability derivatives, Notional amount	$ 2,938	$ 3,192
Total asset derivatives, Number of contracts | contract	4,727	3,929
Total liability derivatives, Number of contracts | contract	3,645	3,331
Total asset derivatives, Fair value, net	$ 50	$ 89
Asset derivatives, Gross asset	51	89
Asset derivatives, Gross liability	(1)	0
Derivative liabilities net amount on balance sheet	(312)	(353)
Liability derivatives, Gross asset	1	2
Liability derivatives, Gross liability	(313)	(355)
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	45	85
Total asset derivatives, Fair value, net	6	3
Asset derivatives, Gross asset	6	3
Asset derivatives, Gross liability	0	0
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	19	50
Derivative liabilities net amount on balance sheet	4	(1)
Liability derivatives, Gross asset	4	0
Liability derivatives, Gross liability	0	(1)
Interest rate swaption agreements | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
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 | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	42	163
Total asset derivatives, Fair value, net	0	2
Asset derivatives, Gross asset	0	2
Asset derivatives, Gross liability	0	0
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	72	0
Derivative liabilities net amount on balance sheet	1	0
Liability derivatives, Gross asset	1	0
Liability derivatives, Gross liability	0	0
Interest rate swap agreements | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
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
Other contracts | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount	3	3
Total asset derivatives, Fair value, net	1	1
Asset derivatives, Gross asset	1	1
Asset derivatives, Gross liability	0	0
Options and warrants | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 0	$ 0
Total asset derivatives, Number of contracts | contract	3,730	3,225
Total asset derivatives, Fair value, net	$ 44	$ 83
Asset derivatives, Gross asset	44	83
Asset derivatives, Gross liability	0	0
Financial futures contracts - Equity and index contracts | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 0	$ 0
Total asset derivatives, Number of contracts | contract	997	704
Total asset derivatives, Fair value, net	$ 1	$ 1
Asset derivatives, Gross asset	1	1
Asset derivatives, Gross liability	0	$ 0
Financial futures contracts - Equity and index contracts | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Number of contracts | contract		200
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	81	$ 57
Total asset derivatives, Fair value, net	1	0
Asset derivatives, Gross asset	1	0
Asset derivatives, Gross liability	0	0
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount		36
Derivative liabilities net amount on balance sheet		1
Liability derivatives, Gross asset		1
Liability derivatives, Gross liability		0
Options and futures | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	$ 0	$ 0
Total liability derivatives, Number of contracts | contract	3,645	3,131
Derivative liabilities net amount on balance sheet	$ (6)	$ (22)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(6)	(22)
Guaranteed accumulation benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	481	615
Derivative liabilities net amount on balance sheet	(38)	(32)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(38)	(32)
Guaranteed withdrawal benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	332	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 | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	1,781	1,786
Derivative liabilities net amount on balance sheet	(247)	(278)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(247)	(278)
Other embedded derivative financial instruments | Derivatives not designated as accounting hedging instruments | Contractholder funds
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 | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	51	19
Total asset derivatives, Fair value, net	2	0
Asset derivatives, Gross asset	3	0
Asset derivatives, Gross liability	(1)	0
Credit default swaps - buying protection | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	2	49
Derivative liabilities net amount on balance sheet	0	(1)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	0	(1)
Credit default swaps – selling protection | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	80	80
Total asset derivatives, Fair value, net	1	2
Asset derivatives, Gross asset	1	2
Asset derivatives, Gross liability	0	0
Credit default swaps – selling protection | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	100	100
Derivative liabilities net amount on balance sheet	(8)	(9)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	$ (8)	$ (9)