Business Combinations - Estimated Fair Values of Aggregate Assets and Liabilities Acquired (Details) $ in Millions	Jun. 30, 2022 USD ($)
Fair Value Of Assets And Liabilities Statement [Line Items]
Cash	$ 3.2
Fiduciary cash	40.5
Fiduciary receivables	12.5
Other current assets	2.9
Fixed assets	1.9
Goodwill	421.4
Other assets	1.9
Total assets acquired	616.5
Fiduciary liabilities	(53.0)
Other current liabilities	(14.3)
Deferred income tax, net	(30.2)
Total liabilities assumed	(97.5)
Net assets acquired	519.0
Orchid Intermediate Holdings L P
Fair Value Of Assets And Liabilities Statement [Line Items]
Cash	3.2
Fiduciary cash	40.5
Fiduciary receivables	12.5
Other current assets	2.7
Fixed assets	1.8
Goodwill	399.3
Other assets	1.7
Total assets acquired	580.9
Fiduciary liabilities	(53.0)
Other current liabilities	(10.7)
Deferred income tax, net	(30.2)
Total liabilities assumed	(93.9)
Net assets acquired	487.0
Other Acquisitions
Fair Value Of Assets And Liabilities Statement [Line Items]
Other current assets	0.2
Fixed assets	0.1
Goodwill	22.1
Other assets	0.2
Total assets acquired	35.6
Other current liabilities	(3.6)
Total liabilities assumed	(3.6)
Net assets acquired	32.0
Purchased Customer Accounts
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	131.5
Purchased Customer Accounts | Orchid Intermediate Holdings L P
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	119.2
Purchased Customer Accounts | Other Acquisitions
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	12.3
Non-compete Agreements
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	0.7
Non-compete Agreements | Other Acquisitions
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	$ 0.7