Investments (excluding Consolidated Investment Entities) - Debt Maturities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, including securities pledged, Amortized Cost	$ 35,955	$ 35,836
Fixed maturities, including securities pledged, Fair Value	37,584	39,663
Fixed maturities
Available-for-sale Securities, Including Securities Pledged [Line Items]
One year or less, Amortized Cost	1,224
One year or less, Fair Value	1,227
After one year through five years, Amortized Cost	5,035
After one year through five years, Fair Value	5,019
After five years through ten years, Amortized Cost	7,998
After five years through ten years, Fair Value	8,117
After ten years, Amortized Cost	14,742
After ten years, Fair Value	16,668
Fixed maturities, including securities pledged, Amortized Cost	40,226	39,807
Fixed maturities, including securities pledged, Fair Value	$ 41,994	$ 43,778
Mortgage-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Percent collateralized mortgage backed securities including interest-only strip or principal-only strip	44.70%	43.40%
Without single maturity date, Amortized Cost	$ 9,144
Without single maturity date, Fair Value	9,091
Other asset-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Without single maturity date, Amortized Cost	2,083
Without single maturity date, Fair Value	1,872
Fixed maturities, including securities pledged, Amortized Cost	2,083	$ 2,058
Fixed maturities, including securities pledged, Fair Value	$ 1,872	$ 2,055