Investments - Mortgage Loans Credit Ratings Indicator (Details) - Commercial Real Estate - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	$ 1,047	$ 1,213
2020
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	46
2019
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	96	93
2018
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	94	93
2017
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	150	221
2016
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	101	140
Prior
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	560	666
1
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	59	58
1 | 2020
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0
1 | 2019
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
1 | 2018
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
1 | 2017
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	22	15
1 | 2016
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
1 | Prior
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	37	43
2 to 4
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	952	1,143
2 to 4 | 2020
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	46
2 to 4 | 2019
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	96	93
2 to 4 | 2018
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	91	93
2 to 4 | 2017
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	124	206
2 to 4 | 2016
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	101	140
2 to 4 | Prior
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	494	611
5 and 6
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	36	12
5 and 6 | 2020
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0
5 and 6 | 2019
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
5 and 6 | 2018
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	3	0
5 and 6 | 2017
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	4	0
5 and 6 | 2016
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
5 and 6 | Prior
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	29	12
7
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
7 | 2020
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0
7 | 2019
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
7 | 2018
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
7 | 2017
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
7 | 2016
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	0	0
7 | Prior
Mortgage Loans on Real Estate [Line Items]
Mortgage loans	$ 0	$ 0