Debt - Schedule of Debt (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Debt - Schedule of Debt (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2023	Dec. 12, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Outstanding Balance		$ 8,092		$ 6,472
Fair Value		7,536		5,467
Asset Management
Debt Instrument [Line Items]
Outstanding Balance		3,883		2,814
Fair Value		3,876		2,574
Amortization of note discount	$ 16	34
Asset Management \| Senior Notes \| 4.00%, 2024 Senior Notes
Debt Instrument [Line Items]
Outstanding Balance		499		499
Fair Value		$ 496		$ 486
Interest rate		4.00%		4.00%
Asset Management \| Senior Notes \| 4.40%, 2026 Senior Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 498		$ 498
Fair Value		$ 490		$ 476
Interest rate		4.40%		4.40%
Asset Management \| Senior Notes \| 4.87%, 2029 Senior Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 675		$ 675
Fair Value		$ 664		$ 639
Interest rate		4.87%		4.87%
Asset Management \| Senior Notes \| 2.65% 2030 Senior Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 496		$ 495
Fair Value		$ 432		$ 407
Interest rate		2.65%		2.65%
Asset Management \| Senior Notes \| 6.38% 2033 Senior Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 492		$ 0
Fair Value		$ 539		$ 0
Interest rate		6.38%		6.38%
Asset Management \| Senior Notes \| 5.00%, 2048 Senior Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 297		$ 297
Fair Value		$ 275		$ 262
Interest rate		5.00%		5.00%
Asset Management \| Subordinated Notes \| 4.95%, 2050 Senior Subordinated Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 297		$ 297
Fair Value		$ 283		$ 252
Interest rate		4.95%		4.95%
Asset Management \| Subordinated Notes \| 7.63% 2053 Subordinated Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 584		$ 0
Fair Value		$ 652		$ 0
Interest rate		7.63%		7.63%
Asset Management \| Secured Debt \| 1.70% Secured Borrowing II
Debt Instrument [Line Items]
Outstanding Balance		$ 14		$ 18
Fair Value		$ 14		$ 17
Interest rate		1.70%		1.70%
Asset Management \| Line of Credit \| 1.30% 2016 AMI Term Facility I
Debt Instrument [Line Items]
Outstanding Balance		$ 19		$ 18
Fair Value		$ 19		$ 18
Interest rate		1.30%		1.30%
Asset Management \| Line of Credit \| 2.00% 2016 AMI Term Facility II
Debt Instrument [Line Items]
Outstanding Balance		$ 12		$ 17
Fair Value		$ 12		$ 17
Interest rate		2.00%		2.00%
Retirement Services
Debt Instrument [Line Items]
Outstanding Balance		$ 4,209		$ 3,658
Fair Value		3,660		2,893
Retirement Services \| Senior Notes \| 4.13% 2028 Notes
Debt Instrument [Line Items]
Outstanding Balance		1,066		1,081
Fair Value		$ 956		$ 921
Interest rate		4.13%		4.13%
Retirement Services \| Senior Notes \| 6.15% 2030 Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 593		$ 606
Fair Value		$ 516		$ 508
Interest rate		6.15%		6.15%
Retirement Services \| Senior Notes \| 3.50% 2031 Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 523		$ 526
Fair Value		$ 442		$ 413
Interest rate		3.50%		3.50%
Retirement Services \| Senior Notes \| 6.65% 2033 Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 395		$ 395
Fair Value		$ 427		$ 398
Interest rate		6.65%		6.65%
Retirement Services \| Senior Notes \| 5.88% 2034 Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 583		$ 0
Fair Value		$ 607		$ 0
Interest rate		5.88%	5.875%	5.88%
Retirement Services \| Senior Notes \| 3.95% 2051 Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 545		$ 546
Fair Value		$ 375		$ 342
Interest rate		3.95%		3.95%
Retirement Services \| Senior Notes \| 3.45% 2052 Notes
Debt Instrument [Line Items]
Outstanding Balance		$ 504		$ 504
Fair Value		$ 337		$ 311
Interest rate		3.45%		3.45%