Investments (Investment Income Net of Related Expenses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 677	$ 702	$ 1,960	$ 1,912
Investment expense	(23)	(23)	(67)	(69)
Investment income, net of related expenses	654	679	1,893	1,843
Available-for-sale Securities [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	483	464	1,437	1,307
Equity securities
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	2	1	5	3
Mortgage Loans on Real Estate [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	66	67	199	187
Policy loans
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	13	14	42	43
Funds withheld at interest
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	95	82	217	210
Short-term Investments [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	1	7	7	21
Other invested assets
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 17	$ 67	$ 53	$ 141