Investments - Mortgage Loans Credit Ratings Indicator (Details) - Commercial Real Estate - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Mortgage loans	$ 1,213	$ 1,361
1
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Mortgage loans	58	42
2 to 4
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Mortgage loans	1,143	1,301
5 and 6
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Mortgage loans	12	18
7
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Mortgage loans	$ 0	$ 0