Business Combinations - Estimated Fair Values of Aggregate Assets and Liabilities Acquired (Details) $ in Millions	Mar. 31, 2022 USD ($)
Fair Value Of Assets And Liabilities Statement [Line Items]
Cash and equivalents	$ 3.2
Fiduciary cash	40.5
Fiduciary receivables	12.5
Other current assets	3.9
Fixed assets	0.6
Goodwill	404.6
Other assets	1.8
Total assets acquired	588.3
Fiduciary liabilities	(53.0)
Other current liabilities	(14.6)
Deferred income tax, net	(30.2)
Total liabilities assumed	(97.8)
Net assets acquired	490.5
Orchid Intermediate Holdings, L.P.
Fair Value Of Assets And Liabilities Statement [Line Items]
Cash and equivalents	3.2
Fiduciary cash	40.5
Fiduciary receivables	12.5
Other current assets	3.4
Fixed assets	0.6
Goodwill	400.6
Other assets	1.8
Total assets acquired	581.8
Fiduciary liabilities	(53.0)
Other current liabilities	(11.6)
Deferred income tax, net	(30.2)
Total liabilities assumed	(94.8)
Net assets acquired	487.0
Other Acquisitions
Fair Value Of Assets And Liabilities Statement [Line Items]
Other current assets	0.5
Goodwill	4.0
Total assets acquired	6.5
Other current liabilities	(3.0)
Total liabilities assumed	(3.0)
Net assets acquired	3.5
Purchased Customer Accounts
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	120.9
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	1.7
Non-compete Agreements
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	0.3
Non-compete Agreements | Other Acquisitions
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	$ 0.3