Investments (held-to-maturity credit quality indicator) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 10,550	$ 11,697
Fixed Maturities Percent of Total Amortized cost	100.00%	100.00%
Standard & Poor's, AAA Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 2,216	$ 2,511
Fixed Maturities Percent of Total Amortized cost	21.00%	22.00%
Standard & Poor's, AA Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 5,479	$ 6,193
Fixed Maturities Percent of Total Amortized cost	52.00%	53.00%
Standard & Poor's, A Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 2,011	$ 2,138
Fixed Maturities Percent of Total Amortized cost	19.00%	18.00%
Standard & Poor's, BBB Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 815	$ 826
Fixed Maturities Percent of Total Amortized cost	8.00%	7.00%
Standard & Poor's, BB Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 28	$ 28
Fixed Maturities Percent of Total Amortized cost	0.00%	0.00%
Other [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 1	$ 1
Fixed Maturities Percent of Total Amortized cost	0.00%	0.00%