Derivative Financial Instruments - Narrative (Details) $ in Millions		3 Months Ended		9 Months Ended
	Nov. 30, 2017 shares	Sep. 30, 2018 USD ($) contract	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) contract	Sep. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($) contract	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 16, 2014 USD ($)
Derivative [Line Items]
Fair Value		$ 449		$ 449
Fair value of assets		2,357		2,357		$ 1,961	$ 1,785
Derivative, Gain (Loss) on Derivative, Net		$ (3)		$ (37)
Other derivatives and embedded derivatives
Derivative [Line Items]
Term of contract, term one				1 year
Term of contract, term two				2 years
Term of contract, term three				3 years
Term of contract, term four				5 years
Futures contracts
Derivative [Line Items]
Number of instruments held | contract		1,029,000,000		1,029,000,000
Other invested assets | Other derivatives and embedded derivatives
Derivative [Line Items]
Fair Value		$ 17		$ 17
Derivative Instruments [Member] | Foreign Exchange Forward [Member]
Derivative [Line Items]
Fair Value		1		1
Derivative Instruments [Member] | Call options
Derivative [Line Items]
Fair Value		431		431
Derivative Instruments [Member] | Futures contracts
Derivative [Line Items]
Fair Value		0		0
Derivatives For Trading And Investment | Not Designated as Hedging Instrument | Call options
Derivative [Line Items]
Fair Value		431		431			492
Derivative notional amount		11,905		11,905			10,577
Collateral posted		377		377			467
Maximum amount of loss due to credit risk		54		54			25
Cash and Cash Equivalents | Not Designated as Hedging Instrument | Call options
Derivative [Line Items]
Collateral posted		288		288
Other Investments Asset | Other invested assets
Derivative [Line Items]
Fixed maturities securities, available-for-sale, at fair value		25		25						$ 35
Other Investments Asset | Other invested assets | Other derivatives and embedded derivatives
Derivative [Line Items]
Derivative notional amount										$ 11
Merrill Lynch [Member] | Derivatives For Trading And Investment | Not Designated as Hedging Instrument | Call options
Derivative [Line Items]
Fair Value		129		129			150
Derivative notional amount		3,515		3,515			2,780
Collateral posted		89		89			118
Maximum amount of loss due to credit risk		40		40			32
Predecessor
Derivative [Line Items]
Fair Value							509
Fair value of assets			$ 1,449		$ 1,449			$ 1,440	$ 1,427
Derivative, Gain (Loss) on Derivative, Net			(8)		(28)
Predecessor | Foreign Exchange Forward [Member]
Derivative [Line Items]
Fair Value							$ 0
Predecessor | Futures contracts
Derivative [Line Items]
Number of instruments held | contract							1,754,000,000
Collateral held		6		6			$ 8
Predecessor | Other invested assets | Other derivatives and embedded derivatives
Derivative [Line Items]
Fair Value							17
Predecessor | Derivative Instruments [Member] | Call options
Derivative [Line Items]
Fair Value							492
Predecessor | Derivative Instruments [Member] | Futures contracts
Derivative [Line Items]
Fair Value							0
Predecessor | Derivatives For Trading And Investment | Not Designated as Hedging Instrument | Call options
Derivative [Line Items]
Collateral posted							467
Maximum amount of loss due to credit risk			25		25
Predecessor | Cash and Cash Equivalents | Not Designated as Hedging Instrument | Call options
Derivative [Line Items]
Collateral posted							$ 349
Preferred Stock
Derivative [Line Items]
Preferred Stock, Call Features, Minimum Term	5 years
Preferred stock dividend rate	10.00%
Series A Cumulative Preferred Stock [Member] | Preferred Stock
Derivative [Line Items]
Stock Issued During Period, Shares, New Issues | shares	275,000
Series B Cumulative Preferred Stock [Member] | Preferred Stock
Derivative [Line Items]
Stock Issued During Period, Shares, New Issues | shares	100,000
Net investment (losses) gains | Foreign Exchange Forward [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net		1	0	1
Net investment (losses) gains | Other derivatives and embedded derivatives
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net		0	1	0
Net investment (losses) gains | Call options
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net		153	113	86
Net investment (losses) gains | Futures contracts
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net		$ 8		$ 8
Net investment (losses) gains | Predecessor | Foreign Exchange Forward [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net					0
Net investment (losses) gains | Predecessor | Other derivatives and embedded derivatives
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net					3
Net investment (losses) gains | Predecessor | Call options
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net					299
Net investment (losses) gains | Predecessor | Futures contracts
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net			$ 5		$ 10