Investments - Loans by U.S. Region (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Open Option Contracts Written [Line Items]
Commercial mortgage loans	$ 4,664	$ 4,919
% of Total	100.00%	100.00%
Pacific
Open Option Contracts Written [Line Items]
Commercial mortgage loans	$ 944	$ 994
% of Total	20.20%	20.20%
South Atlantic
Open Option Contracts Written [Line Items]
Commercial mortgage loans	$ 966	$ 1,011
% of Total	20.70%	20.50%
Middle Atlantic
Open Option Contracts Written [Line Items]
Commercial mortgage loans	$ 1,019	$ 1,039
% of Total	21.90%	21.20%
West South Central
Open Option Contracts Written [Line Items]
Commercial mortgage loans	$ 537	$ 566
% of Total	11.50%	11.50%
Mountain
Open Option Contracts Written [Line Items]
Commercial mortgage loans	$ 442	$ 458
% of Total	9.50%	9.30%
East North Central
Open Option Contracts Written [Line Items]
Commercial mortgage loans	$ 383	$ 465
% of Total	8.20%	9.50%
New England
Open Option Contracts Written [Line Items]
Commercial mortgage loans	$ 84	$ 75
% of Total	1.80%	1.50%
West North Central
Open Option Contracts Written [Line Items]
Commercial mortgage loans	$ 212	$ 258
% of Total	4.50%	5.20%
East South Central
Open Option Contracts Written [Line Items]
Commercial mortgage loans	$ 77	$ 53
% of Total	1.70%	1.10%