Investments - Mortgage Loans Credit Ratings Indicator (Details) - Commercial Real Estate - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	$ 997	$ 1,047
Category 1
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	58	59
Category 2 to 4
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	904	952
Categories 5 and 6
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	35	36
Category 7
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
2021
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	30
2021 | Category 1
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0
2021 | Category 2 to 4
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	30
2021 | Categories 5 and 6
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0
2021 | Category 7
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0
2020
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	48	46
2020 | Category 1
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
2020 | Category 2 to 4
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	48	46
2020 | Categories 5 and 6
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
2020 | Category 7
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
2019
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	97	96
2019 | Category 1
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
2019 | Category 2 to 4
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	97	96
2019 | Categories 5 and 6
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
2019 | Category 7
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
2018
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	78	94
2018 | Category 1
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
2018 | Category 2 to 4
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	75	91
2018 | Categories 5 and 6
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	3	3
2018 | Category 7
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
2017
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	138	150
2017 | Category 1
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	22	22
2017 | Category 2 to 4
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	112	124
2017 | Categories 5 and 6
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	4	4
2017 | Category 7
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
Prior
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	606	661
Prior | Category 1
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	36	37
Prior | Category 2 to 4
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	542	595
Prior | Categories 5 and 6
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	28	29
Prior | Category 7
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	$ 0	$ 0