Derivatives - Derivative Balance Sheet Classification (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Notional Amount	$ 36,485	$ 37,756
Fair Value	(440)	(438)
Asset Derivatives	336	470
Liability Derivatives	(776)	(908)
Fixed maturities, available-for-sale
Derivatives, Fair Value [Line Items]
Notional Amount	39	39
Fair Value	0	0
Asset Derivatives	0	0
Liability Derivatives	0	0
Other investments
Derivatives, Fair Value [Line Items]
Notional Amount	4,346	10,340
Fair Value	40	135
Asset Derivatives	44	149
Liability Derivatives	(4)	(14)
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	18,389	12,754
Fair Value	(491)	(588)
Asset Derivatives	263	231
Liability Derivatives	(754)	(819)
Reinsurance Recoverable Including Reinsurance Premium Paid [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	3,048	3,233
Fair Value	29	90
Asset Derivatives	29	90
Liability Derivatives	0	0
Other Policyholder Funds and Benefits Payable [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	10,663	11,390
Fair Value	(18)	(75)
Asset Derivatives	0	0
Liability Derivatives	(18)	(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	36,485	36,088
Fair Value	(440)	(426)
Asset Derivatives	336	464
Liability Derivatives	(776)	(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	26	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
Interest Rate Swaps and Futures [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	4,618	3,219
Fair Value	(320)	(356)
Asset Derivatives	149	203
Liability Derivatives	(469)	(559)
Foreign Currency Swaps and Forwards [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	222	342
Fair Value	(12)	(6)
Asset Derivatives	5	0
Liability Derivatives	(17)	(6)
Three Win Related Foreign Currency Swaps [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	540	540
Fair Value	(167)	(170)
Asset Derivatives	0	0
Liability Derivatives	(167)	(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	380	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	56	200
Fair Value	0	1
Asset Derivatives	6	7
Liability Derivatives	(6)	(6)
GMWB Product Derivatives [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	10,663	11,390
Fair Value	(18)	(75)
Asset Derivatives	0	0
Liability Derivatives	(18)	(75)
GMWB Reinsurance [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	2,239	2,372
Fair Value	22	35
Asset Derivatives	22	35
Liability Derivatives	0	0
GMWB Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	8,434	9,452
Fair Value	40	67
GMWB Hedging Instruments [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	8,434	9,452
Fair Value	40	67
Asset Derivatives	99	116
Liability Derivatives	(59)	(49)
Macro Hedge Program [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	8,479	7,252
Fair Value	3	23
Asset Derivatives	42	45
Liability Derivatives	(39)	(22)
Coinsurance and Modified Coinsurance Reinsurance Contracts [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	809	861
Fair Value	7	55
Asset Derivatives	7	55
Liability Derivatives	0	0
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)