Investments (Net Investment Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 5,178	$ 5,041	$ 4,888
Investment expense	(334)	(281)	(257)
Net investment income	4,844	4,760	4,631
Fixed Maturity Securities [Member] | AFS Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	4,129	4,048	4,019
Equity AFS Securities [Member] | AFS Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income		12	11
Trading Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	79	88	94
Equity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	4
Mortgage Loans On Real Estate [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	492	433	413
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	122	134	139
Invested Cash [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	23	11	12
Commercial Mortgage Loan Prepayment And Bond Make Whole Premiums [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	78	138	115
Alternative Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	222	165	75
Consent Fees [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	4	6	5
Other Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 24	$ 5	$ 4