Derivatives - Additional Information (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	$ 36,485,000,000	$ 37,756,000,000
Derivative, Fair Value, Net	(440,000,000)	(438,000,000)
Cash collateral held	277,000,000	310,000,000
Pledged collateral, securities	4,000,000	6,000,000
Margin Deposit Assets	121,000,000	136,000,000
Securities collateral held	4,000,000
Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	36,485,000,000	36,088,000,000
Derivative, Fair Value, Net	(440,000,000)	(426,000,000)
Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	0	1,668,000,000
Derivative, Fair Value, Net	0	(12,000,000)
Swap [Member] | GMWB Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	4,617,000,000	5,023,000,000
Swap [Member] | Fair Value Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Fair Value, Net	44,000,000	59,000,000
Equity Contract [Member] | GMWB Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	751,000,000	1,407,000,000
Equity Contract [Member] | Fair Value Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Fair Value, Net	(30,000,000)	(31,000,000)
Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount		2,700,000,000
Interest rate swaps | GMWB Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	3,066,000,000	3,022,000,000
Interest rate swaps | Fair Value Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Fair Value, Net	26,000,000	39,000,000
Interest rate swaps | Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	2,700,000,000
Interest rate swaps | Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	0	1,486,000,000
Derivative, Fair Value, Net	0	0
GMWB Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	8,434,000,000	9,452,000,000
Derivative, Fair Value, Net	40,000,000	67,000,000
GMWB Hedging Instruments [Member] | Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	8,434,000,000	9,452,000,000
Derivative, Fair Value, Net	40,000,000	67,000,000
Collateral Pledged [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Pledged collateral, securities	$ 686,000,000	$ 729,000,000