Investments (Net Investment Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 5,366	$ 5,178	$ 5,041
Investment expense	(404)	(334)	(281)
Net investment income	4,962	4,844	4,760
Fixed Maturity Securities [Member] | AFS Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	4,214	4,129	4,048
Equity AFS Securities [Member] | AFS Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income			12
Trading Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	187	79	88
Equity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	4	4
Mortgage Loans On Real Estate [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	626	492	433
Real estate [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	1	1	1
Policy loans [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	128	122	134
Cash And Invested Cash [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	33	23	11
Commercial Mortgage Loan Prepayment And Bond Make Whole Premiums [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	115	78	138
Alternative investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	24	222	165
Consent fees [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	7	4	6
Other Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 27	$ 24	$ 5