Investments (Investment Income Net of Related Expenses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	$ 2,667	$ 2,616	$ 2,229
Investment Income, Investment Expense	(92)	(96)	(90)
Investment income, net of related expenses	2,575	2,520	2,139
Available-for-sale Securities [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	1,928	1,786	1,529
Equity Securities [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	6	8	4
Mortgage Loans on Real Estate [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	282	255	214
Policy Loans [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	56	58	59
Funds Withheld At Interest [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	279	297	310
Short-term Investments [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	7	28	14
Other Aggregated Investments [Member]
Major Categories Of Investment Income Net Of Expenses [Line Items]
Gross Investment Income, Operating	$ 109	$ 184	$ 99