Derivative Financial Instruments and Off-balance sheet Financial Instruments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) contract	Dec. 31, 2015 USD ($) contract
Derivatives, Fair Value
Assumed recoveries under sale of credit protection	$ 0
Securities pledged in the form of margin deposits	2
Total asset derivatives, Notional amount	395	$ 302
Total liability derivatives, Notional amount	2,524	2,957
Total derivatives, Notional amount	$ 2,919	$ 3,259
Total asset derivatives, Number of contracts | contract	3,923	4,727
Total liability derivatives, Number of contracts | contract	3,928	3,645
Total derivatives, Number of contracts | contract	7,851	8,372
Total asset derivatives, Fair value, net	$ 101	$ 56
Asset derivatives, Gross asset	103	57
Asset derivatives, Gross liability	(2)	(1)
Derivative liabilities net amount on balance sheet	(329)	(308)
Total derivatives, Fair value, net	(228)	(252)
Liability derivatives, Gross asset	0	5
Liability derivatives, Gross liability	(329)	(313)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	346	257
Total liability derivatives, Notional amount	$ 2,524	$ 2,938
Total asset derivatives, Number of contracts | contract	3,923	4,727
Total liability derivatives, Number of contracts | contract	3,928	3,645
Total asset derivatives, Fair value, net	$ 96	$ 50
Asset derivatives, Gross asset	98	51
Asset derivatives, Gross liability	(2)	(1)
Derivative liabilities net amount on balance sheet	(329)	(312)
Liability derivatives, Gross asset	0	1
Liability derivatives, Gross liability	(329)	(313)
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	49	45
Total asset derivatives, Fair value, net	5	6
Asset derivatives, Gross asset	5	6
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
Derivative liabilities net amount on balance sheet		4
Liability derivatives, Gross asset		4
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	65	42
Total asset derivatives, Fair value, net	1	0
Asset derivatives, Gross asset	1	0
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	3,917	3,730
Total asset derivatives, Fair value, net	$ 87	$ 44
Asset derivatives, Gross asset	87	44
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	6	997
Total asset derivatives, Fair value, net	$ 0	$ 1
Asset derivatives, Gross asset	0	1
Asset derivatives, Gross liability	0	0
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	173	81
Total asset derivatives, Fair value, net	7	1
Asset derivatives, Gross asset	8	1
Asset derivatives, Gross liability	(1)	0
Credit default swaps - buying protection | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	25	51
Total asset derivatives, Fair value, net	(1)	2
Asset derivatives, Gross asset	0	3
Asset derivatives, Gross liability	(1)	(1)
Credit default swaps - buying protection | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	6	2
Derivative liabilities net amount on balance sheet	0	0
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	0	0
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	1
Asset derivatives, Gross asset	1	1
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	(3)	(8)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(3)	(8)
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
Interest rate swap agreements | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount		85
Derivative liabilities net amount on balance sheet		0
Liability derivatives, Gross asset		0
Liability derivatives, Gross liability		0
Interest rate swaption agreements | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount		72
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	3,928	3,645
Derivative liabilities net amount on balance sheet	$ (37)	$ (6)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(37)	(6)
Guaranteed accumulation benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	391	481
Derivative liabilities net amount on balance sheet	(34)	(38)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(34)	(38)
Guaranteed withdrawal benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	290	332
Derivative liabilities net amount on balance sheet	(9)	(14)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(9)	(14)
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	1,737	1,781
Derivative liabilities net amount on balance sheet	(246)	(247)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	$ (246)	(247)
Other embedded derivative financial instruments | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount		85
Derivative liabilities net amount on balance sheet		0
Liability derivatives, Gross asset		0
Liability derivatives, Gross liability		$ 0