Variable Interest Entities - Consolidated VIEs (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 305,046.7	$ 290,867.0
Total liabilities	293,836.1	280,587.2
Redeemable noncontrolling interest	248.9	262.0	$ 332.5	$ 255.6
Aggregate consolidated variable interest entities
Carrying amounts of consolidated VIE assets and liabilities
Total assets	37,511.3	37,220.5
Total liabilities	34,778.5	34,614.9
Redeemable noncontrolling interest	226.4	235.3
Mandatory retirement savings funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	35,034.4	34,876.9
Total liabilities	34,688.3	34,528.3
Real estate VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	829.1	689.6
Total liabilities	63.0	42.2
Sponsored investment funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	523.8	471.4
Total liabilities	6.3	2.6
Redeemable noncontrolling interest	226.4	235.3
Residential mortgage loans VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	874.7	1,182.6
Total liabilities	20.9	$ 41.8
Asset-backed limited partnership
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 249.3