Investments (excluding Consolidated Investment Entities) - Debt Maturities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, including securities pledged, Amortized Cost Basis	$ 35,836	$ 36,268
Fixed maturities, including securities pledged	39,663	36,897
Fixed maturities
Available-for-sale Securities, Including Securities Pledged [Line Items]
One year or less, Amortized Cost	1,105
One year or less, Fair Value	1,120
After one year through five years, Amortized Cost	5,391
After one year through five years, Fair Value	5,638
After five years through ten years, Amortized Cost	8,014
After five years through ten years, Fair Value	8,667
After ten years, Amortized Cost	14,838
After ten years, Fair Value	17,520
Fixed maturities, including securities pledged, Amortized Cost Basis	39,807	39,937
Fixed maturities, including securities pledged	$ 43,778	$ 40,592
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	43.40%	46.00%
Without single maturity date, Amortized Cost	$ 8,401
Without single maturity date, Fair Value	8,778
Other asset-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Without single maturity date, Amortized Cost	2,058
Without single maturity date, Fair Value	2,055
Fixed maturities, including securities pledged, Amortized Cost Basis	2,058	$ 1,688
Fixed maturities, including securities pledged	$ 2,055	$ 1,658