Investments (excluding Consolidated Investment Entities) - Fixed Maturities (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	$ 35,955	$ 35,836
Fixed maturities, including securities pledged, Fair Value	37,584	39,663
Securities pledged, amortized costs	1,416	1,264
U.S. Treasuries
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	1,076	1,074
Fixed maturities, Gross Unrealized Capital Gains	519	308
Fixed maturities, Gross Unrealized Capital Losses	0	0
Embedded Derivatives	0	0
Fixed maturities, including securities pledged, Fair Value	1,595	1,382
OTTI	0	0
U.S. Government agencies and authorities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	73	74
Fixed maturities, Gross Unrealized Capital Gains	27	21
Fixed maturities, Gross Unrealized Capital Losses	0	0
Embedded Derivatives	0	0
Fixed maturities, including securities pledged, Fair Value	100	95
OTTI	0	0
State, municipalities and political subdivisions
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	1,213	1,220
Fixed maturities, Gross Unrealized Capital Gains	105	103
Fixed maturities, Gross Unrealized Capital Losses	3	0
Embedded Derivatives	0	0
Fixed maturities, including securities pledged, Fair Value	1,315	1,323
OTTI	0	0
U.S. corporate public securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	12,721	12,980
Fixed maturities, Gross Unrealized Capital Gains	1,537	1,977
Fixed maturities, Gross Unrealized Capital Losses	302	19
Embedded Derivatives	0	0
Fixed maturities, including securities pledged, Fair Value	13,956	14,938
OTTI	0	0
U.S. corporate private securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	5,519	5,568
Fixed maturities, Gross Unrealized Capital Gains	254	488
Fixed maturities, Gross Unrealized Capital Losses	130	21
Embedded Derivatives	0	0
Fixed maturities, including securities pledged, Fair Value	5,643	6,035
OTTI	0	0
Foreign corporate public securities and foreign governments
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	3,875	3,887
Fixed maturities, Gross Unrealized Capital Gains	251	460
Fixed maturities, Gross Unrealized Capital Losses	120	6
Embedded Derivatives	0	0
Fixed maturities, including securities pledged, Fair Value	4,006	4,341
OTTI	0	0
Foreign corporate private securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	4,522	4,545
Fixed maturities, Gross Unrealized Capital Gains	87	288
Fixed maturities, Gross Unrealized Capital Losses	189	2
Embedded Derivatives	0	0
Fixed maturities, including securities pledged, Fair Value	4,416	4,831
OTTI	4	0
Residential mortgage-backed
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	5,515	4,999
Fixed maturities, Gross Unrealized Capital Gains	227	200
Fixed maturities, Gross Unrealized Capital Losses	162	14
Embedded Derivatives	27	19
Fixed maturities, including securities pledged, Fair Value	5,607	5,204
OTTI	0	5
Commercial mortgage-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	3,629	3,402
Fixed maturities, Gross Unrealized Capital Gains	186	176
Fixed maturities, Gross Unrealized Capital Losses	330	4
Embedded Derivatives	0	0
Fixed maturities, including securities pledged, Fair Value	3,484	3,574
OTTI	1	0
Other asset-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	2,083	2,058
Fixed maturities, Gross Unrealized Capital Gains	9	22
Fixed maturities, Gross Unrealized Capital Losses	218	25
Embedded Derivatives	0	0
Fixed maturities, including securities pledged, Fair Value	1,872	2,055
OTTI	2	1
Fixed maturities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Fixed maturities, amortized cost	40,226	39,807
Fixed maturities, Gross Unrealized Capital Gains	3,202	4,043
Fixed maturities, Gross Unrealized Capital Losses	1,454	91
Embedded Derivatives	27	19
Fixed maturities, including securities pledged, Fair Value	41,994	43,778
OTTI	7	6
Total fixed maturities, less securities pledged, Amortized Cost	38,810	38,543
Total fixed maturities, less securities pledged, Gross Unrealized Capital Gains	3,001	3,889
Total fixed maturities, less securities pledged, Gross Unrealized Capital Losses	1,392	81
Total fixed maturities, less securities pledged, Fair Value	40,439	42,370
Impaired available-for-sale securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Net unrealized gains on impaired available-for-sale securities		336
Collateral Pledged
Available-for-sale Securities, Including Securities Pledged [Line Items]
Securities pledged	1,555	1,408
Collateral Pledged | Fixed maturities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Embedded Derivatives	0	0
OTTI	0	0
Securities pledged, amortized costs	1,416	1,264
Securities pledged, Gross Unrealized Capital Gains	201	154
Securities pledged, Gross Unrealized Capital Losses	62	10
Securities pledged	$ 1,555	$ 1,408