Investments (excluding Consolidated Investment Entities) - Debt Maturities (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	$ 36,209	$ 35,836
Fixed maturities, available-for-sale, at fair value	40,938	39,663
Fixed maturities
Available-for-sale Securities, Including Securities Pledged [Line Items]
One year or less, Amortized Cost	1,273
One year or less, Fair Value	1,281
After one year through five years, Amortized Cost	4,991
After one year through five years, Fair Value	5,259
After five years through ten years, Amortized Cost	7,814
After five years through ten years, Fair Value	8,652
After ten years, Amortized Cost	14,613
After ten years, Fair Value	18,097
Fixed maturities, amortized cost	40,257	39,807
Fixed maturities, available-for-sale, at fair value	45,158	43,778
Mortgage-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Without single maturity date, Amortized Cost	9,444
Without single maturity date, Fair Value	9,793
Other asset-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Without single maturity date, Amortized Cost	2,122
Without single maturity date, Fair Value	2,076
Fixed maturities, amortized cost	2,122	2,058
Fixed maturities, available-for-sale, at fair value	$ 2,076	$ 2,055