Variable Interest Entities - Consolidated VIEs (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 308,683.5	$ 305,046.7
Total liabilities	297,082.3	293,836.1
Redeemable noncontrolling interest	370.8	248.9	$ 272.7	$ 262.0
Aggregate consolidated variable interest entities
Carrying amounts of consolidated VIE assets and liabilities
Total assets	35,589.3	37,511.3
Total liabilities	32,598.5	34,778.5
Redeemable noncontrolling interest	343.9	226.4
Mandatory retirement savings funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	32,840.8	35,034.4
Total liabilities	32,516.4	34,688.3
Real estate VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	869.5	829.1
Total liabilities	49.6	63.0
Sponsored investment funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	770.6	523.8
Total liabilities	11.9	6.3
Redeemable noncontrolling interest	343.9	226.4
Residential mortgage loans VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	859.7	874.7
Total liabilities	20.6	20.9
Asset-backed limited partnership
Carrying amounts of consolidated VIE assets and liabilities
Total assets	248.7	249.3
Unfunded commitments	$ 0.0	$ 0.0