Acquisitions - Summary of Allocation of Purchase Price for Acquisitions of Acquiree (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Funds receivable and funds held on behalf of clients	$ 2,450.8	$ 2,079.1
Goodwill	9,218.1	8,969.5	$ 8,863.0
Battea
Business Acquisition [Line Items]
Accounts receivable	40.3
Property, plant and equipment	1.9
Other assets	3.0
Funds receivable and funds held on behalf of clients	284.8
Operating lease right-of-use assets	1.2
Goodwill	325.7
Accrued employee compensation and other liabilities	(68.8)
Deferred income taxes	(33.9)
Client Funds Obligations	(284.8)
Consideration paid, net of cash acquired	645.6
Iress Managed Funds Administration Business
Business Acquisition [Line Items]
Accounts receivable		2.2
Property, plant and equipment		0.0
Other assets		0.6
Funds receivable and funds held on behalf of clients		0.0
Operating lease right-of-use assets		0.0
Goodwill		21.6
Accrued employee compensation and other liabilities		(1.3)
Deferred income taxes		(3.9)
Client Funds Obligations		0.0
Consideration paid, net of cash acquired		32.9
Acquired Client Relationships and Contracts [Member] | Battea
Business Acquisition [Line Items]
Intangible assets acquired	246.6	11.5
Completed Technology [Member] | Battea
Business Acquisition [Line Items]
Intangible assets acquired	121.8	2.2
Trade Names [Member] | Battea
Business Acquisition [Line Items]
Intangible assets acquired	$ 7.8	$ 0.0