Insurance Subsidiaries - Schedule of Surplus Notes (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
7.979% Security Life of Denver Insurance Company, due 2029
Schedule of Surplus Notes [Line Items]
Surplus Notes	$ 35	$ 35
6.257% Security Life of Denver International Limited, due 2034
Schedule of Surplus Notes [Line Items]
Surplus Notes	50	50
6.257% ReliaStar Life Insurance Company, due 2034
Schedule of Surplus Notes [Line Items]
Surplus Notes	175	175
6.257% Voya Retirement Insurance and Annuity Company, due 2034
Schedule of Surplus Notes [Line Items]
Surplus Notes	$ 175	$ 175