Investments - Principal geographic distribution of commercial real estate exceeding 5% of the mortgage loans portfolio (Details) $ in Millions	Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($)
Schedule of Available for Sale Securities
Number of loans | loan	246
Mortgage loans, net | $	$ 4,075	$ 4,817
Mortgage loans on real estate, carrying value (percentage)	100.00%	100.00%
2021 | Mortgage loans
Schedule of Available for Sale Securities
Number of loans | loan	28
Mortgage loans, net | $	$ 277
Mortgage loans on real estate, carrying value (percentage)	6.80%
2022 | Mortgage loans
Schedule of Available for Sale Securities
Number of loans | loan	25
Mortgage loans, net | $	$ 388
Mortgage loans on real estate, carrying value (percentage)	9.50%
2023 | Mortgage loans
Schedule of Available for Sale Securities
Number of loans | loan	42
Mortgage loans, net | $	$ 556
Mortgage loans on real estate, carrying value (percentage)	13.70%
2024 | Mortgage loans
Schedule of Available for Sale Securities
Number of loans | loan	27
Mortgage loans, net | $	$ 637
Mortgage loans on real estate, carrying value (percentage)	15.60%
Thereafter | Mortgage loans
Schedule of Available for Sale Securities
Number of loans | loan	124
Mortgage loans, net | $	$ 2,217
Mortgage loans on real estate, carrying value (percentage)	54.40%
Apartment complex
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	37.80%	36.80%
Office buildings
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	23.20%	22.60%
Warehouse
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	14.60%	16.80%
Retail
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	13.90%	13.40%
Other
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	10.50%	10.40%
Texas
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	20.60%	16.90%
California
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	14.60%	15.10%
Florida
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	6.80%	6.40%
Illinois
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	6.10%	7.10%
North Carolina
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	5.10%	4.50%
New Jersey
Schedule of Available for Sale Securities
Mortgage loans on real estate, carrying value (percentage)	3.50%	5.60%