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	$ 5,271	$ 5,169	$ 5,032
Investment expense	(186)	(179)	(158)
Net investment income	5,085	4,990	4,874
Fixed Maturity AFS Securities [Member] | AFS Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	4,209	4,163	4,138
Equity 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	84	94	100
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	496	440	422
Real estate [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	1	2	2
Policy loans [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	123	135	140
Invested Cash [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	26	11	14
Commercial mortgage loan prepayment and bond makewhole premiums [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	79	139	120
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	$ 23	$ 2	$ 5