Variable Interest Entities - Consolidated VIEs (Details) - USD ($) $ in Millions	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 352,752.3		$ 341,376.5
Total liabilities	339,862.8		328,985.2
Redeemable noncontrolling interest	711.7	$ 544.1	474.3	$ 391.2	$ 326.7	$ 337.7
Aggregate consolidated variable interest entities
Carrying amounts of consolidated VIE assets and liabilities
Total assets	46,579.0		44,585.2
Total liabilities	43,394.8		41,519.8
Redeemable noncontrolling interest	672.1		440.9
Mandatory retirement savings funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	43,756.7		41,865.2
Total liabilities	43,323.8		41,450.5
Real estate VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	916.2		883.4
Total liabilities	27.3		34.2
Sponsored investment funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	1,116.0		851.4
Total liabilities	25.1		16.3
Redeemable noncontrolling interest	672.1		440.9
Residential mortgage loans VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	682.6		728.9
Total liabilities	18.6		18.8
Asset-backed limited partnership
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 107.5		$ 256.3