Investments (excluding Consolidated Investment Entities) - Unrealized Capital Losses (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) security	Dec. 31, 2018 USD ($) security
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve Months or Less Below Amortized Cost, Fair Value	$ 1,823	$ 14,386
Twelve Months or Less Below Amortized Cost, Unrealized Capital Losses	21	549
More Than Twelve Months Below Amortized Cost, Fair Value	1,450	3,375
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	70	298
Total Fair Value	3,273	17,761
Total Unrealized Capital Losses	$ 91	$ 847
Total number of securities in an unrealized loss position, Twelve Months or Less Below Amortized Cost, Fair Value | security	334	2,177
Total number of securities in an unrealized loss position, More Than Twelve Months Below Amortized Cost, Fair Value | security	338	686
Total number of securities in an unrealized loss position, Total, Fair Value | security	672	2,863
Available-for-sale Securities, change in loss position	$ 756
Fair value decline below amortized cost greater than 20%
Available-for-sale Securities, Including Securities Pledged [Line Items]
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	$ 12
Total number of securities in an unrealized loss position, More Than Twelve Months Below Amortized Cost, Fair Value | security	8
U.S. Treasuries
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve Months or Less Below Amortized Cost, Fair Value	$ 2	$ 0
Twelve Months or Less Below Amortized Cost, Unrealized Capital Losses	0	0
More Than Twelve Months Below Amortized Cost, Fair Value	21	40
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	0	1
Total Fair Value	23	40
Total Unrealized Capital Losses	0	1
State, municipalities, and political subdivisions
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve Months or Less Below Amortized Cost, Fair Value	25	363
Twelve Months or Less Below Amortized Cost, Unrealized Capital Losses	0	7
More Than Twelve Months Below Amortized Cost, Fair Value	1	178
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	0	9
Total Fair Value	26	541
Total Unrealized Capital Losses	0	16
U.S. corporate public securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve Months or Less Below Amortized Cost, Fair Value	122	5,010
Twelve Months or Less Below Amortized Cost, Unrealized Capital Losses	3	220
More Than Twelve Months Below Amortized Cost, Fair Value	199	742
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	16	80
Total Fair Value	321	5,752
Total Unrealized Capital Losses	19	300
U.S. corporate private securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve Months or Less Below Amortized Cost, Fair Value	113	2,031
Twelve Months or Less Below Amortized Cost, Unrealized Capital Losses	1	56
More Than Twelve Months Below Amortized Cost, Fair Value	195	744
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	20	86
Total Fair Value	308	2,775
Total Unrealized Capital Losses	21	142
Foreign corporate public securities and foreign governments
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve Months or Less Below Amortized Cost, Fair Value	15	1,849
Twelve Months or Less Below Amortized Cost, Unrealized Capital Losses	0	88
More Than Twelve Months Below Amortized Cost, Fair Value	103	253
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	6	41
Total Fair Value	118	2,102
Total Unrealized Capital Losses	6	129
Foreign corporate private securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve Months or Less Below Amortized Cost, Fair Value	36	1,969
Twelve Months or Less Below Amortized Cost, Unrealized Capital Losses	0	101
More Than Twelve Months Below Amortized Cost, Fair Value	78	327
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	2	30
Total Fair Value	114	2,296
Total Unrealized Capital Losses	2	131
Residential mortgage-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve Months or Less Below Amortized Cost, Fair Value	730	795
Twelve Months or Less Below Amortized Cost, Unrealized Capital Losses	8	17
More Than Twelve Months Below Amortized Cost, Fair Value	194	531
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	6	30
Total Fair Value	924	1,326
Total Unrealized Capital Losses	14	47
Commercial mortgage-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve Months or Less Below Amortized Cost, Fair Value	472	1,206
Twelve Months or Less Below Amortized Cost, Unrealized Capital Losses	4	22
More Than Twelve Months Below Amortized Cost, Fair Value	18	484
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	0	19
Total Fair Value	490	1,690
Total Unrealized Capital Losses	4	41
Other asset-backed securities
Available-for-sale Securities, Including Securities Pledged [Line Items]
Twelve Months or Less Below Amortized Cost, Fair Value	308	1,163
Twelve Months or Less Below Amortized Cost, Unrealized Capital Losses	5	38
More Than Twelve Months Below Amortized Cost, Fair Value	641	76
More Than Twelve Months Below Amortized Cost, Unrealized Capital Losses	20	2
Total Fair Value	949	1,239
Total Unrealized Capital Losses	$ 25	$ 40