Derivatives - Derivative Balance Sheet Classification (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Notional Amount	$ 40,345	$ 37,756
Fair Value	(461)	(438)
Asset Derivatives	355	470
Liability Derivatives	(816)	(908)
Fixed maturities, available-for-sale
Derivatives, Fair Value [Line Items]
Notional Amount	41	39
Fair Value	0	0
Asset Derivatives	0	0
Liability Derivatives	0	0
Other investments
Derivatives, Fair Value [Line Items]
Notional Amount	6,486	10,340
Fair Value	76	135
Asset Derivatives	97	149
Liability Derivatives	(21)	(14)
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	20,485	12,754
Fair Value	(575)	(588)
Asset Derivatives	204	231
Liability Derivatives	(779)	(819)
Reinsurance Recoverable Including Reinsurance Premium Paid [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	2,988	3,233
Fair Value	26	90
Asset Derivatives	26	90
Liability Derivatives	0	0
Other Policyholder Funds and Benefits Payable [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	10,345	11,390
Fair Value	12	(75)
Asset Derivatives	28	0
Liability Derivatives	(16)	(75)
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	0	1,668
Fair Value	0	(12)
Asset Derivatives	0	6
Liability Derivatives	0	(18)
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	40,345	36,088
Fair Value	(461)	(426)
Asset Derivatives	355	464
Liability Derivatives	(816)	(890)
Interest rate swaps
Derivatives, Fair Value [Line Items]
Notional Amount		2,700
Interest rate swaps | Fair Value Hedging [Member]
Derivatives, Fair Value [Line Items]
Fair Value	16	39
Interest rate swaps | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	0	1,486
Fair Value	0	0
Asset Derivatives	0	1
Liability Derivatives	0	(1)
Interest rate swaps | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	2,700
Currency Swap [Member] | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	0	182
Fair Value	0	(12)
Asset Derivatives	0	5
Liability Derivatives	0	(17)
Interest Rate Swaps and Futures [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	4,694	3,219
Fair Value	(292)	(356)
Asset Derivatives	123	203
Liability Derivatives	(415)	(559)
Foreign Currency Swaps and Forwards [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	225	342
Fair Value	(10)	(6)
Asset Derivatives	6	0
Liability Derivatives	(16)	(6)
Three Win Related Foreign Currency Swaps [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	539	540
Fair Value	(180)	(170)
Asset Derivatives	0	0
Liability Derivatives	(180)	(170)
Credit derivatives that purchase credit protection | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	45	80
Fair Value	(1)	(3)
Asset Derivatives	0	0
Liability Derivatives	(1)	(3)
Credit derivatives that assume credit risk | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	292	380
Fair Value	6	3
Asset Derivatives	6	3
Liability Derivatives	0	0
Credit Derivatives in Offsetting Positions [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	48	200
Fair Value	0	1
Asset Derivatives	5	7
Liability Derivatives	(5)	(6)
GMWB Product Derivatives [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	10,345	11,390
Fair Value	12	(75)
Asset Derivatives	28	0
Liability Derivatives	(16)	(75)
GMWB Reinsurance [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	2,188	2,372
Fair Value	16	35
Asset Derivatives	16	35
Liability Derivatives	0	0
GMWB Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	8,527	9,452
Fair Value	16	67
GMWB Hedging Instruments [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	8,527	9,452
Fair Value	16	67
Asset Derivatives	83	116
Liability Derivatives	(67)	(49)
Macro Hedge Program [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	12,642	7,252
Fair Value	(38)	23
Asset Derivatives	78	45
Liability Derivatives	(116)	(22)
Coinsurance and Modified Coinsurance Reinsurance Contracts [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	800	861
Fair Value	10	55
Asset Derivatives	10	55
Liability Derivatives	$ 0	$ 0