Investments (Investment Income Net of Related Expenses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 667	$ 609	$ 1,283	$ 1,210
Investment expense	(22)	(25)	(44)	(46)
Investment income, net of related expenses	645	584	1,239	1,164
Available-for-sale Securities [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	474	428	954	843
Equity securities
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	1	1	3	2
Mortgage Loans on Real Estate [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	66	61	133	120
Policy loans
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	14	14	29	29
Funds withheld at interest
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	69	66	122	128
Short-term Investments [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	2	7	6	14
Other invested assets
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 41	$ 32	$ 36	$ 74