Derivative Instruments - Derivatives - Derivative Balance Sheet Classification (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 12,025	$ 13,706
Fair Value	(60)	(66)
Asset Derivatives	32	40
Liability Derivatives	(92)	(106)
Fixed maturities, available-for-sale
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	251	244
Fair Value	0	0
Asset Derivatives	0	0
Liability Derivatives	0	0
Other investments
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,381	1,277
Fair Value	12	12
Asset Derivatives	12	13
Liability Derivatives	0	(1)
Other liabilities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	10,393	12,185
Fair Value	(72)	(78)
Asset Derivatives	20	27
Liability Derivatives	(92)	(105)
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	9,416	11,396
Fair Value	(67)	(65)
Asset Derivatives	22	36
Liability Derivatives	(89)	(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	7,600
Foreign currency swaps \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	269	270
Fair Value	6	(1)
Asset Derivatives	9	3
Liability Derivatives	(3)	(4)
Total cash flow hedges
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,609	2,310
Fair Value	7	(1)
Asset Derivatives	10	4
Liability Derivatives	(3)	(5)
Interest rate swaps and futures \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	8,334	9,338
Fair Value	(79)	(59)
Asset Derivatives	5	3
Liability Derivatives	(84)	(62)
Foreign currency swaps and forwards \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	251	464
Fair Value	0	(1)
Asset Derivatives	0	0
Liability Derivatives	0	(1)
Credit derivatives that purchase credit protection \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	5	124
Fair Value	0	(3)
Asset Derivatives	0	0
Liability Derivatives	0	(3)
Credit derivatives that assume credit risk \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	600	500
Fair Value	12	13
Asset Derivatives	12	13
Liability Derivatives	0	0
Credit derivatives in offsetting positions \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	222	29
Fair Value	0	0
Asset Derivatives	5	5
Liability Derivatives	(5)	(5)
Equity index swaps and options \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4	941
Fair Value	0	(15)
Asset Derivatives	0	15
Liability Derivatives	$ 0	$ (30)

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

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