Derivative Instruments - Derivatives - Derivative Balance Sheet Classification (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Notional Amount	$ 13,201	$ 12,291
Fair Value	(59)	(61)
Asset Derivatives	35	31
Liability Derivatives	(94)	(92)
Fixed maturities, available-for-sale
Derivatives, Fair Value [Line Items]
Notional Amount	225	153
Fair Value	0	0
Asset Derivatives	0	0
Liability Derivatives	0	0
Other investments
Derivatives, Fair Value [Line Items]
Notional Amount	1,305	9,864
Fair Value	12	7
Asset Derivatives	15	23
Liability Derivatives	(3)	(16)
Other liabilities
Derivatives, Fair Value [Line Items]
Notional Amount	11,671	2,274
Fair Value	(71)	(68)
Asset Derivatives	20	8
Liability Derivatives	(91)	(76)
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	10,919	10,098
Fair Value	(66)	(56)
Asset Derivatives	26	27
Liability Derivatives	(92)	(83)
Interest rate swaps | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	2,040	2,040
Fair Value	0	1
Asset Derivatives	0	2
Liability Derivatives	0	(1)
Interest rate swaps | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	7,600	7,100
Foreign currency swaps | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	242	153
Fair Value	7	(6)
Asset Derivatives	9	2
Liability Derivatives	(2)	(8)
Total cash flow hedges
Derivatives, Fair Value [Line Items]
Notional Amount	2,282	2,193
Fair Value	7	(5)
Asset Derivatives	9	4
Liability Derivatives	(2)	(9)
Interest rate swaps and futures | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	8,844	8,451
Fair Value	(70)	(62)
Asset Derivatives	2	8
Liability Derivatives	(72)	(70)
Foreign currency swaps and forwards | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	454	287
Fair Value	1	(1)
Asset Derivatives	1	0
Liability Derivatives	0	(1)
Credit derivatives that purchase credit protection | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	353	6
Fair Value	(2)	0
Asset Derivatives	0	0
Liability Derivatives	(2)	0
Credit derivatives that assume credit risk | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	521	1,102
Fair Value	10	3
Asset Derivatives	10	8
Liability Derivatives	0	(5)
Credit derivatives in offsetting positions | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	32	41
Fair Value	0	0
Asset Derivatives	5	6
Liability Derivatives	(5)	(6)
Equity index swaps and options | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	715	211
Fair Value	(5)	4
Asset Derivatives	8	5
Liability Derivatives	$ (13)	$ (1)