Variable Interest Entities - Consolidated VIEs (Details) - USD ($) $ in Millions	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 287,948.0		$ 290,578.3
Total liabilities	276,965.6		280,298.5
Redeemable noncontrolling interest	259.5	$ 266.7	262.0	$ 255.1	$ 268.5	$ 332.5
Aggregate consolidated variable interest entities
Carrying amounts of consolidated VIE assets and liabilities
Total assets	35,748.2		37,220.5
Total liabilities	32,933.3		34,614.9
Redeemable noncontrolling interest	237.1		235.3
Mandatory retirement savings funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	33,189.6		34,876.9
Total liabilities	32,847.0		34,528.3
Real estate VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	844.0		689.6
Total liabilities	52.6		42.2
Sponsored investment funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	516.7		471.4
Total liabilities	10.6		2.6
Redeemable noncontrolling interest	237.1		235.3
Residential mortgage loans VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	1,082.9		1,182.6
Total liabilities	23.1		$ 41.8
Asset-backed limited partnership
Carrying amounts of consolidated VIE assets and liabilities
Total assets	115.0
Unfunded commitments	$ 135.0