Derivative Instruments - Derivatives - Derivative Balance Sheet Classification (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Notional Amount	$ 12,511	$ 12,291
Fair Value	(40)	(61)
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	38	31
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	78	92
Fixed maturities, available-for-sale
Derivatives, Fair Value [Line Items]
Notional Amount	153	153
Fair Value	0	0
Asset Derivatives	0	0
Liability Derivatives	0	0
Other investments
Derivatives, Fair Value [Line Items]
Notional Amount	1,951	9,864
Fair Value	24	7
Asset Derivatives	27	23
Liability Derivatives	(3)	(16)
Other liabilities
Derivatives, Fair Value [Line Items]
Notional Amount	10,407	2,274
Fair Value	(64)	(68)
Asset Derivatives	11	8
Liability Derivatives	(75)	(76)
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	10,296	10,098
Fair Value	(33)	(56)
Asset Derivatives	36	27
Liability Derivatives	(69)	(83)
Interest rate swaps \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	2,040	2,040
Fair Value	(2)	1
Asset Derivatives	1	2
Liability Derivatives	(3)	(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	175	153
Fair Value	(5)	(6)
Asset Derivatives	1	2
Liability Derivatives	(6)	(8)
Total cash flow hedges
Derivatives, Fair Value [Line Items]
Notional Amount	2,215	2,193
Fair Value	(7)	(5)
Asset Derivatives	2	4
Liability Derivatives	(9)	(9)
Interest rate swaps and futures \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	8,336	8,451
Fair Value	(53)	(62)
Asset Derivatives	9	8
Liability Derivatives	(62)	(70)
Foreign currency swaps and forwards \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	384	287
Fair Value	0	(1)
Asset Derivatives	1	0
Liability Derivatives	(1)	(1)
Credit derivatives that purchase credit protection \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	5	6
Fair Value	0	0
Asset Derivatives	0	0
Liability Derivatives	0	0
Credit derivatives that assume credit risk \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	810	1,102
Fair Value	19	3
Asset Derivatives	19	8
Liability Derivatives	0	(5)
Credit derivatives in offsetting positions \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	38	41
Fair Value	0	0
Asset Derivatives	6	6
Liability Derivatives	(6)	(6)
Equity index swaps and options \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	723	211
Fair Value	1	4
Asset Derivatives	1	5
Liability Derivatives	$ 0	$ (1)

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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