Derivative Financial Instruments (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) contract	Dec. 31, 2015 USD ($) contract
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Assumed recoveries under sale of credit protection	$ 0
Securities pledged in the form of margin deposits	8
Derivatives, Fair Value
Total asset derivatives, Notional amount	127	$ 302
Total liability derivatives, Notional amount	3,028	2,957
Total derivatives, Notional amount	$ 3,155	$ 3,259
Total asset derivatives, Number of contracts | contract	4,505	4,727
Total liability derivatives, Number of contracts | contract	3,638	3,645
Total derivatives, Number of contracts | contract	8,143	8,372
Total asset derivatives	$ 56	$ 56
Total liability derivatives	(332)	(308)
Total derivatives, Fair value, net	(276)	(252)
Asset derivatives, Gross asset	56	57
Asset derivatives, Gross liability	0	(1)
Liability derivatives, Gross asset	6	5
Liability derivatives, Gross liability	(338)	(313)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	112	257
Total liability derivatives, Notional amount	$ 2,979	$ 2,938
Total asset derivatives, Number of contracts | contract	4,505	4,727
Total liability derivatives, Number of contracts | contract	3,638	3,645
Total asset derivatives	$ 53	$ 50
Total liability derivatives	(336)	(312)
Asset derivatives, Gross asset	53	51
Asset derivatives, Gross liability	0	(1)
Liability derivatives, Gross asset	2	1
Liability derivatives, Gross liability	(338)	(313)
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	15	45
Total asset derivatives	3	6
Asset derivatives, Gross asset	3	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	49	19
Total liability derivatives	4	4
Liability derivatives, Gross asset	4	4
Liability derivatives, Gross liability	0	0
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	24	42
Total asset derivatives	0	0
Asset derivatives, Gross asset	0	0
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	66	72
Total liability derivatives	1	1
Liability derivatives, Gross asset	1	1
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
Total liability derivatives	0	0
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	0	0
Options | 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	3,762	3,730
Total asset derivatives	$ 51	$ 44
Asset derivatives, Gross asset	51	44
Asset derivatives, Gross liability	0	0
Financial futures 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	743	997
Total asset derivatives	$ 0	$ 1
Asset derivatives, Gross asset	0	1
Asset derivatives, Gross liability	0	0
Options | 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	3,638	3,645
Total liability derivatives	$ (11)	$ (6)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(11)	(6)
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount		81
Total asset derivatives		1
Asset derivatives, Gross asset		1
Asset derivatives, Gross liability		0
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	104
Total liability derivatives	(4)
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	(4)
Guaranteed accumulation benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	423	481
Total liability derivatives	(49)	(38)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(49)	(38)
Guaranteed withdrawal benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	292	332
Total liability derivatives	(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 | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	1,766	1,781
Total liability derivatives	(245)	(247)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(245)	(247)
Other embedded derivative financial instruments | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	85	85
Total liability derivatives	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	5	51
Total asset derivatives	0	2
Asset derivatives, Gross asset	0	3
Asset derivatives, Gross liability	0	(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	58	2
Total liability derivatives	0	0
Liability derivatives, Gross asset	1	0
Liability derivatives, Gross liability	(1)	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	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
Total liability derivatives	(9)	(8)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(9)	(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	1	1
Asset derivatives, Gross asset	1	1
Asset derivatives, Gross liability	$ 0	$ 0