Investments Investments (held-to-maturity credit quality indicator) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 12,070	$ 12,581
Fixed Maturities Percent of Total Amortized cost	100.00%
Standard & Poor's, AAA Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 2,642
Fixed Maturities Percent of Total Amortized cost	22.00%
Standard & Poor's, AA Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 6,608
Fixed Maturities Percent of Total Amortized cost	55.00%
Standard & Poor's, A Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 2,371
Fixed Maturities Percent of Total Amortized cost	20.00%
Standard & Poor's, BBB Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 422
Fixed Maturities Percent of Total Amortized cost	3.00%
Standard & Poor's, BB Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 21
Fixed Maturities Percent of Total Amortized cost	0.00%
Other [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 6
Fixed Maturities Percent of Total Amortized cost	0.00%