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Business Combinations - Schedule of Purchase Price Allocation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition
Goodwill	$ 2,689.2	$ 2,661.4	$ 2,651.7
Parnassus & Abacus
Business Acquisition
Consideration paid	363.0
Deferred obligations	211.6
Contingent payment obligations	18.1
Lease contract	(0.8)
Tangible assets, net	2.7
Goodwill	30.5
Total purchase price	994.4
Parnassus & Abacus | Acquired client relationships
Business Acquisition
Intangible assets	957.0
Parnassus & Abacus | Trade name
Business Acquisition
Intangible assets	5.0
Parnassus & Abacus | Affiliated Managers Group, Inc. and Coinvestor
Business Acquisition
Consideration paid	462.6
Deferred obligations	261.1
Contingent payment obligations	23.7
Retained equity interests	247.0
Enterprise value	$ 994.4

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