Derivatives - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	$ 40,345	$ 37,756
Derivative, Fair Value, Net	(461)	(438)
Pledged collateral, securities	4	6
Margin Deposit Assets	115	136
Cash collateral held	280	310
Securities collateral held	3
Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	40,345	36,088
Derivative, Fair Value, Net	(461)	(426)
Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	0	1,668
Derivative, Fair Value, Net	0	(12)
Swap [Member] \| GMWB Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	4,627	5,023
Swap [Member] \| Fair Value Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Fair Value, Net	32	59
Equity Contract [Member] \| GMWB Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	824	1,407
Equity Contract [Member] \| Fair Value Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Fair Value, Net	(32)	(31)
Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount		2,700
Interest rate swaps \| GMWB Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	3,076	3,022
Interest rate swaps \| Fair Value Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Fair Value, Net	16	39
Interest rate swaps \| Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	2,700
Interest rate swaps \| Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	0	1,486
Derivative, Fair Value, Net	0	0
GMWB Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	8,527	9,452
Derivative, Fair Value, Net	16	67
GMWB Hedging Instruments [Member] \| Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	8,527	9,452
Derivative, Fair Value, Net	16	67
Collateral Pledged [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Pledged collateral, securities	$ 748	$ 729

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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The amount of cash or securities placed with a broker or counterparty as security for a trading or derivatives securities position which was partially obtained with funds provided by the broker dealer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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The carrying value as of the balance sheet date of the assets received as collateral against securities loaned to other broker-dealers. Borrowers of securities generally are required to provide collateral to the lenders of securities, commonly cash but sometimes other securities or standby letters of credit, with a value slightly higher than that of the securities borrowed. In instances where the entity is permitted to sell or re-pledge these securities, the entity reports the fair value of the collateral received and the related obligation to return the collateral as a liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-SubTopic 30
-Section 50
-Paragraph 1A
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Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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