Derivative Instruments - Derivatives - Derivative Balance Sheet Classification (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 11,854	$ 13,706
Fair Value	(56)	(66)
Asset Derivatives	47	40
Liability Derivatives	(103)	(106)
Fixed maturities, available-for-sale
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	253	244
Fair Value	0	0
Asset Derivatives	0	0
Liability Derivatives	0	0
Other investments
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,046	1,277
Fair Value	10	12
Asset Derivatives	13	13
Liability Derivatives	(3)	(1)
Other liabilities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	10,555	12,185
Fair Value	(66)	(78)
Asset Derivatives	34	27
Liability Derivatives	(100)	(105)
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	9,227	11,396
Fair Value	(83)	(65)
Asset Derivatives	20	36
Liability Derivatives	(103)	(101)
Interest rate swaps \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,340	2,040
Fair Value	1	0
Asset Derivatives	1	1
Liability Derivatives	0	(1)
Interest rate swaps \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		7,600
Foreign currency swaps \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	287	270
Fair Value	26	(1)
Asset Derivatives	26	3
Liability Derivatives	0	(4)
Total cash flow hedges
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,627	2,310
Fair Value	27	(1)
Asset Derivatives	27	4
Liability Derivatives	0	(5)
Interest rate swaps and futures \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	8,333	9,338
Fair Value	(89)	(59)
Asset Derivatives	6	3
Liability Derivatives	(95)	(62)
Foreign currency swaps and forwards \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	485	464
Fair Value	1	(1)
Asset Derivatives	2	0
Liability Derivatives	(1)	(1)
Credit derivatives that purchase credit protection \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	122	124
Fair Value	7	(3)
Asset Derivatives	7	0
Liability Derivatives	0	(3)
Credit derivatives that assume credit risk \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	250	500
Fair Value	(2)	13
Asset Derivatives	0	13
Liability Derivatives	(2)	0
Credit derivatives in offsetting positions \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	26	29
Fair Value	0	0
Asset Derivatives	4	5
Liability Derivatives	(4)	(5)
Equity index swaps and options \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	11	941
Fair Value	0	(15)
Asset Derivatives	1	15
Liability Derivatives	$ (1)	$ (30)

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

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Nominal or face amount used to calculate payment on derivative.

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