Derivative Financial Instruments (Details)	9 Months Ended
	Sep. 30, 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	8,000,000
Derivatives, Fair Value
Total asset derivatives, Notional amount	106,000,000	$ 302,000,000
Total liability derivatives, Notional amount	3,082,000,000	2,957,000,000
Total derivatives, Notional amount	$ 3,188,000,000	$ 3,259,000,000
Total asset derivatives, Number of contracts | contract	4,262	4,727
Total liability derivatives, Number of contracts | contract	4,627	3,645
Total derivatives, Number of contracts | contract	8,889	8,372
Total asset derivatives	$ 85,000,000	$ 56,000,000
Total liability derivatives	(337,000,000)	(308,000,000)
Total derivatives, Fair value, net	(252,000,000)	(252,000,000)
Asset derivatives, Gross asset	85,000,000	57,000,000
Asset derivatives, Gross liability	0	(1,000,000)
Liability derivatives, Gross asset	5,000,000	5,000,000
Liability derivatives, Gross liability	(342,000,000)	(313,000,000)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	106,000,000	257,000,000
Total liability derivatives, Notional amount	$ 3,033,000,000	$ 2,938,000,000
Total asset derivatives, Number of contracts | contract	4,262	4,727
Total liability derivatives, Number of contracts | contract	4,627	3,645
Total asset derivatives	$ 85,000,000	$ 50,000,000
Total liability derivatives	(341,000,000)	(312,000,000)
Asset derivatives, Gross asset	85,000,000	51,000,000
Asset derivatives, Gross liability	0	(1,000,000)
Liability derivatives, Gross asset	1,000,000	1,000,000
Liability derivatives, Gross liability	(342,000,000)	(313,000,000)
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount		45,000,000
Total asset derivatives		6,000,000
Asset derivatives, Gross asset		6,000,000
Asset derivatives, Gross liability		0
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	49,000,000	19,000,000
Total liability derivatives	4,000,000	4,000,000
Liability derivatives, Gross asset	4,000,000	4,000,000
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	23,000,000	42,000,000
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	44,000,000	72,000,000
Total liability derivatives	1,000,000	1,000,000
Liability derivatives, Gross asset	1,000,000	1,000,000
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	85,000,000	85,000,000
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	4,210	3,730
Total asset derivatives	$ 83,000,000	$ 44,000,000
Asset derivatives, Gross asset	83,000,000	44,000,000
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	52	997
Total asset derivatives	$ 0	$ 1,000,000
Asset derivatives, Gross asset	0	1,000,000
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	4,627	3,645
Total liability derivatives	$ (26,000,000)	$ (6,000,000)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(26,000,000)	(6,000,000)
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount		81,000,000
Total asset derivatives		1,000,000
Asset derivatives, Gross asset		1,000,000
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	173,000,000
Total liability derivatives	(2,000,000)
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	(2,000,000)
Guaranteed accumulation benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	420,000,000	481,000,000
Total liability derivatives	(38,000,000)	(38,000,000)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(38,000,000)	(38,000,000)
Guaranteed withdrawal benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	299,000,000	332,000,000
Total liability derivatives	(13,000,000)	(14,000,000)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(13,000,000)	(14,000,000)
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	1,741,000,000	1,781,000,000
Total liability derivatives	(255,000,000)	(247,000,000)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(255,000,000)	(247,000,000)
Other embedded derivative financial instruments | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	85,000,000	85,000,000
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		51,000,000
Total asset derivatives		2,000,000
Asset derivatives, Gross asset		3,000,000
Asset derivatives, Gross liability		(1,000,000)
Credit default swaps – buying protection | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	86,000,000	2,000,000
Total liability derivatives	(4,000,000)	0
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(4,000,000)	0
Credit default swaps – selling protection | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	80,000,000	80,000,000
Total asset derivatives	1,000,000	1,000,000
Asset derivatives, Gross asset	1,000,000	1,000,000
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	100,000,000	100,000,000
Total liability derivatives	(4,000,000)	(8,000,000)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(4,000,000)	(8,000,000)
Other contracts | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount	3,000,000	3,000,000
Total asset derivatives	1,000,000	1,000,000
Asset derivatives, Gross asset	1,000,000	1,000,000
Asset derivatives, Gross liability	$ 0	$ 0