Variable Interest Entities - Consolidated VIEs (Details) - USD ($) $ in Millions	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 323,103.8		$ 313,663.6
Total liabilities	311,245.3		302,194.6
Redeemable noncontrolling interest	391.2	$ 326.7	337.7	$ 277.4	$ 370.8	$ 248.9
Aggregate consolidated variable interest entities
Carrying amounts of consolidated VIE assets and liabilities
Total assets	39,985.5		35,834.9
Total liabilities	37,033.4		33,051.8
Redeemable noncontrolling interest	363.1		309.9
Mandatory retirement savings funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	37,319.6		33,130.4
Total liabilities	36,950.3		32,802.2
Real estate VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	865.4		814.3
Total liabilities	36.1		69.4
Sponsored investment funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	782.5		833.7
Total liabilities	27.7		160.3
Redeemable noncontrolling interest	363.1		309.9
Residential mortgage loans VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	764.5		806.5
Total liabilities	19.3		19.9
Asset-backed limited partnership
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 253.5		$ 250.0