Derivative Instruments (Non Hedging Derivatives and Embedded Derivatives Effect on Income Statement) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ 91	$ (170)	$ 168
Other revenues	(392)	(363)	(352)
Gain Loss On Investments Related To Change In Fair Value Of Derivatives Excluding Embedded Derivatives	4	0	(43)
Interest credited	(697)	(425)	(502)
Not Designated as Hedging Instrument [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(37)	(1)	54
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	65	(21)	11
Not Designated as Hedging Instrument [Member] | Future [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(46)	21	(36)
Not Designated as Hedging Instrument [Member] | Currency Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	0	(4)	0
Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	1	0	1
Not Designated as Hedging Instrument [Member] | Consumer Price Index Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(18)	(10)	(2)
Not Designated as Hedging Instrument [Member] | Credit Default Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	30	(2)	18
Not Designated as Hedging Instrument [Member] | Equity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(40)	7	(43)
Not Designated as Hedging Instrument [Member] | Longevity Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Other revenues	(13)	(9)	(9)
Not Designated as Hedging Instrument [Member] | Mortality Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Other revenues	(1)	0	(1)
Not Designated as Hedging Instrument [Member] | Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	11	(13)	145
Not Designated as Hedging Instrument [Member] | Embedded Derivatives In Indexed Annuity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Interest credited	(57)	(27)	(80)
Not Designated as Hedging Instrument [Member] | Embedded Derivatives In Variable Annuity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ 5	$ (15)	$ 32