Investments (excluding Consolidated Investment Entities) - Loans by U.S. Region (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Open Option Contracts Written [Line Items]
Total Commercial mortgage loans	$ 8,320	$ 8,678
Percentage of Total	100.00%	100.00%
Pacific
Open Option Contracts Written [Line Items]
Total Commercial mortgage loans	$ 2,071	$ 2,078
Percentage of Total	24.90%	23.80%
South Atlantic
Open Option Contracts Written [Line Items]
Total Commercial mortgage loans	$ 1,668	$ 1,771
Percentage of Total	20.10%	20.40%
Middle Atlantic
Open Option Contracts Written [Line Items]
Total Commercial mortgage loans	$ 1,496	$ 1,525
Percentage of Total	18.00%	17.60%
West South Central
Open Option Contracts Written [Line Items]
Total Commercial mortgage loans	$ 857	$ 952
Percentage of Total	10.30%	11.00%
Mountain
Open Option Contracts Written [Line Items]
Total Commercial mortgage loans	$ 898	$ 892
Percentage of Total	10.80%	10.30%
East North Central
Open Option Contracts Written [Line Items]
Total Commercial mortgage loans	$ 733	$ 833
Percentage of Total	8.80%	9.60%
New England
Open Option Contracts Written [Line Items]
Total Commercial mortgage loans	$ 161	$ 154
Percentage of Total	1.90%	1.80%
West North Central
Open Option Contracts Written [Line Items]
Total Commercial mortgage loans	$ 336	$ 390
Percentage of Total	4.00%	4.50%
East South Central
Open Option Contracts Written [Line Items]
Total Commercial mortgage loans	$ 100	$ 83
Percentage of Total	1.20%	1.00%