Investments (Net Investment Income) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 5,685	$ 5,454	$ 5,271
Investment expense	(175)	(231)	(186)
Net investment income	5,510	5,223	5,085
Fixed Maturity AFS Securities [Member] \| AFS Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	4,334	4,281	4,209
Trading Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	202	191	84
Equity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	3	4	4
Mortgage Loans On Real Estate [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	677	629	496
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	125	129	123
Invested Cash [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	12	40	26
Commercial mortgage loan prepayment and bond makewhole premiums [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	82	119	79
Alternative investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	197	22	222
Consent fees [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	7	8	4
Other Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 45	$ 30	$ 23

Amount, before investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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