Derivative Financial Instruments (Details)	6 Months Ended
	Jun. 30, 2017 USD ($) contract	Dec. 31, 2016 USD ($) contract
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	23,000,000
Derivatives, Fair Value
Total asset derivatives, notional amount	1,083,000,000	$ 1,103,000,000
Total liability derivatives, notional amount	3,291,000,000	2,673,000,000
Total derivatives, notional amount	$ 4,374,000,000	$ 3,776,000,000
Total asset derivatives, number of contracts | contract	7,317	4,233
Total liability derivatives, number of contracts | contract	8,896	4,848
Total derivatives, Number of contracts | contract	16,213	9,081
Derivative assets net amount on balance sheet	$ 102,000,000	$ 93,000,000
Asset derivatives gross amount	116,000,000	121,000,000
Asset derivatives, gross liability	(14,000,000)	(28,000,000)
Derivative liabilities net amount on balance sheet	(331,000,000)	(334,000,000)
Total derivatives, fair value, net	(229,000,000)	(241,000,000)
Liability derivatives, gross asset	11,000,000	0
Liability derivatives gross amount	(342,000,000)	(334,000,000)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount		1,054,000,000
Total liability derivatives, notional amount	$ 3,242,000,000	$ 2,673,000,000
Total asset derivatives, number of contracts | contract		4,233
Total liability derivatives, number of contracts | contract	8,896	4,848
Derivative assets net amount on balance sheet		$ 88,000,000
Asset derivatives gross amount		116,000,000
Asset derivatives, gross liability		(28,000,000)
Derivative liabilities net amount on balance sheet	$ (333,000,000)	(334,000,000)
Liability derivatives, gross asset	9,000,000	0
Liability derivatives gross amount	(342,000,000)	(334,000,000)
Foreign currency swap agreements | Other investments | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount		49,000,000
Derivative assets net amount on balance sheet		5,000,000
Asset derivatives gross amount		5,000,000
Asset derivatives, gross liability		0
Foreign currency swap agreements | Other liabilities & accrued expenses | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount	49,000,000
Derivative liabilities net amount on balance sheet	2,000,000
Liability derivatives, gross asset	2,000,000
Liability derivatives gross amount	0
Interest rate cap agreements | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	22,000,000	65,000,000
Derivative assets net amount on balance sheet	0	1,000,000
Asset derivatives gross amount	0	1,000,000
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	37,000,000
Derivative liabilities net amount on balance sheet	1,000,000
Liability derivatives, gross asset	1,000,000
Liability derivatives gross amount	0
Options | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	$ 585,000,000	$ 0
Total asset derivatives, number of contracts | contract	6,798	3,972
Derivative assets net amount on balance sheet	$ 110,000,000	$ 88,000,000
Asset derivatives gross amount	113,000,000	88,000,000
Asset derivatives, gross liability	(3,000,000)	0
Financial futures 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	519	261
Derivative assets net amount on balance sheet	$ 0	$ 0
Asset derivatives gross amount	0	0
Asset 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	8,896	4,848
Derivative liabilities net amount on balance sheet	$ (42,000,000)	$ (39,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives gross amount	(42,000,000)	(39,000,000)
Foreign currency forwards | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	344,000,000	759,000,000
Derivative assets net amount on balance sheet	(7,000,000)	0
Asset derivatives gross amount	2,000,000	24,000,000
Asset derivatives, gross liability	(9,000,000)	(24,000,000)
Foreign currency forwards | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount	621,000,000
Derivative liabilities net amount on balance sheet	(2,000,000)
Liability derivatives, gross asset	8,000,000
Liability derivatives gross amount	(10,000,000)
Guaranteed accumulation benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount	246,000,000	391,000,000
Derivative liabilities net amount on balance sheet	(28,000,000)	(34,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives gross amount	(28,000,000)	(34,000,000)
Guaranteed withdrawal benefits | Contractholder funds | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount	282,000,000	290,000,000
Derivative liabilities net amount on balance sheet	(7,000,000)	(9,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives gross amount	(7,000,000)	(9,000,000)
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	1,753,000,000	1,751,000,000
Derivative liabilities net amount on balance sheet	(250,000,000)	(247,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives gross amount	(250,000,000)	(247,000,000)
Credit default swaps – buying protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	49,000,000	87,000,000
Derivative assets net amount on balance sheet	(2,000,000)	(4,000,000)
Asset derivatives gross amount	0	0
Asset derivatives, gross liability	(2,000,000)	(4,000,000)
Credit default swaps – buying protection | Other liabilities & accrued expenses | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total liability derivatives, notional amount	173,000,000	136,000,000
Derivative liabilities net amount on balance sheet	(5,000,000)	(2,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives gross amount	(5,000,000)	(2,000,000)
Credit default swaps – selling protection | Other investments | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	80,000,000	140,000,000
Derivative assets net amount on balance sheet	1,000,000	2,000,000
Asset derivatives gross amount	1,000,000	2,000,000
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	130,000,000	105,000,000
Derivative liabilities net amount on balance sheet	0	(3,000,000)
Liability derivatives, gross asset	0	0
Liability derivatives gross amount	0	(3,000,000)
Other contracts | Other assets | Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, notional amount	3,000,000	3,000,000
Derivative assets net amount on balance sheet	0	1,000,000
Asset derivatives gross amount	0	1,000,000
Asset derivatives, gross liability	$ 0	$ 0