Business Combinations - Estimated Fair Values of Aggregate Assets and Liabilities Acquired (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Fair Value Of Assets And Liabilities Statement [Line Items]
Cash paid	$ 44.7
Other payable	0.2
Recorded earn-out payable	19.6	$ 10.8
Total consideration	64.5
Maximum potential earn-out payable	21.1
Cash and equivalents	3.3
Fiduciary cash	3.8
Fiduciary receivables	3.3
Other current assets	2.6
Fixed assets	0.2
Goodwill	23.0
Intangible assets	16.6
Other assets	0.2
Total assets acquired	53.0
Fiduciary liabilities	(7.1)
Other current liabilities	(3.8)
Deferred income tax, net	23.9
Other long term liabilities	(1.5)
Total liabilities assumed	11.5
Net assets acquired	64.5
Other Acquisitions
Fair Value Of Assets And Liabilities Statement [Line Items]
Cash paid	44.7
Other payable	0.2
Recorded earn-out payable	19.6
Total consideration	64.5
Maximum potential earn-out payable	21.1
Cash and equivalents	3.3
Fiduciary cash	3.8
Fiduciary receivables	3.3
Other current assets	2.6
Fixed assets	0.2
Goodwill	23.0
Intangible assets	16.6
Other assets	0.2
Total assets acquired	53.0
Fiduciary liabilities	(7.1)
Other current liabilities	(3.8)
Deferred income tax, net	23.9
Other long term liabilities	(1.5)
Total liabilities assumed	11.5
Net assets acquired	$ 64.5