Investments (Investment Income Net of Related Expenses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ 616	$ 601
Investment expense	(22)	(21)
Investment income, net of related expenses	594	580
Available-for-sale Securities [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	480	415
Equity Securities [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	2	1
Mortgage Loans on Real Estate [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	67	60
Policy loans
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	15	14
Funds withheld at interest
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	53	62
Short-term Investments [Member]
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	4	7
Other invested assets
Major Categories Of Investment Income Net of Expenses [Line Items]
Investment revenue	$ (5)	$ 42