Derivatives - Derivative Balance Sheet Classification (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Notional Amount	$ 12,291	$ 12,730
Fair Value	(61)	(90)
Asset Derivatives [1]	31	25
Liability Derivatives [1]	(92)	(115)
Fixed maturities, available-for-sale
Derivatives, Fair Value [Line Items]
Notional Amount	153	153
Fair Value	0	0
Asset Derivatives [1]	0	0
Liability Derivatives [1]	0	0
Other investments
Derivatives, Fair Value [Line Items]
Notional Amount	9,864	9,957
Fair Value	7	10
Asset Derivatives [1]	23	16
Liability Derivatives [1]	(16)	(6)
Other liabilities
Derivatives, Fair Value [Line Items]
Notional Amount	2,274	2,620
Fair Value	(68)	(100)
Asset Derivatives [1]	8	9
Liability Derivatives [1]	(76)	(109)
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	2,193	2,343
Fair Value	(5)	(13)
Asset Derivatives [1]	4	1
Liability Derivatives [1]	(9)	(14)
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	10,098	10,387
Fair Value	(56)	(77)
Asset Derivatives [1]	27	24
Liability Derivatives [1]	(83)	(101)
Interest rate swaps | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	2,040	2,190
Fair Value	1	0
Asset Derivatives [1]	2	1
Liability Derivatives [1]	(1)	(1)
Interest rate swaps | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	7,100	7,300
Foreign currency swaps | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	153	153
Fair Value	(6)	(13)
Asset Derivatives [1]	2	0
Liability Derivatives [1]	(8)	(13)
Interest rate swaps and futures | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	8,451	7,986
Fair Value	(62)	(83)
Asset Derivatives [1]	8	7
Liability Derivatives [1]	(70)	(90)
Foreign currency swaps and forwards | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	287	213
Fair Value	(1)	(1)
Asset Derivatives [1]	0	0
Liability Derivatives [1]	(1)	(1)
Credit derivatives that purchase credit protection | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	6	61
Fair Value	0	1
Asset Derivatives [1]	0	2
Liability Derivatives [1]	0	(1)
Credit derivatives that assume credit risk | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	1,102	823
Fair Value	3	3
Asset Derivatives [1]	8	3
Liability Derivatives [1]	(5)	0
Credit derivatives in offsetting positions | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	41	1,046
Fair Value	0	2
Asset Derivatives [1]	6	11
Liability Derivatives [1]	(6)	(9)
Equity index swaps and options | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional Amount	211	258
Fair Value	4	1
Asset Derivatives [1]	5	1
Liability Derivatives [1]	$ (1)	$ 0