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	$ 5,454	$ 5,271	$ 5,169
Investment expense	(231)	(186)	(179)
Net investment income	5,223	5,085	4,990
Fixed Maturity AFS Securities [Member] | AFS Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	4,281	4,209	4,163
Equity 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	191	84	94
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	629	496	440
Real estate [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	1	1	2
Policy loans [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	129	123	135
Invested Cash [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	40	26	11
Commercial mortgage loan prepayment and bond makewhole premiums [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	119	79	139
Alternative investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	22	222	165
Consent fees [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	8	4	6
Other Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 30	$ 23	$ 2