Corporate Investments and Funds Held For Clients (Tables)

12 Months Ended

Dec. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Cash and Cash Equivalents and Investments

The tables below present our cash and cash equivalents, the funds held for clients cash and cash equivalents as well as the investments that were included within funds held for clients on the consolidated balance sheets:

	December 31, 2024
Type of issue	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Cash and cash equivalents	$	402.0	$	—	$	—		$	402.0
Funds held for clients cash and cash equivalents		3,640.8		—		—			3,640.8
Available-for-sale securities(1):
U.S. treasury securities		24.9		—		(0.2	)		24.7
Total investments	$	4,067.7	$	—	$	(0.2	)	$	4,067.5
	December 31, 2023
Type of issue	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Cash and cash equivalents	$	294.0	$	—	$	—		$	294.0
Funds held for clients cash and cash equivalents		2,128.8		—		—			2,128.8
Available-for-sale securities(1):
Certificates of deposit		25.0		—		—			25.0
U.S. treasury securities		174.8		—		(1.2	)		173.6
Total investments	$	2,622.6	$	—	$	(1.2	)	$	2,621.4

(1)All available-for-sale securities were included within the funds held for clients.

Summary of Unrealized Losses and Fair Values of Available-for-Sale Securities that have been in Unrealized Loss Position for Period of Less than and Greater than 12 Months

The unrealized losses and fair values of available-for-sale securities that have been in an unrealized loss position for a period of less than and greater than 12 months as of December 31, 2024, are as follows:

	December 31, 2024
	Securities in unrealized loss position for less than 12 months					Securities in unrealized loss position for greater than 12 months				Total
Type of issue	Gross unrealized losses			Fair value		Gross unrealized losses		Fair value		Gross unrealized losses			Fair value
U.S. treasury securities	$	(0.2	)	$	24.7	$	—	$	—	$	(0.2	)	$	24.7
Total	$	(0.2	)	$	24.7	$	—	$	—	$	(0.2	)	$	24.7

The unrealized losses and fair values of available-for-sale securities that have been in an unrealized loss position for a period of less than and greater than 12 months as of December 31, 2023, are as follows:

	December 31, 2023
	Securities in unrealized loss position for less than 12 months				Securities in unrealized loss position for greater than 12 months					Total
Type of issue	Gross unrealized losses		Fair value		Gross unrealized losses			Fair value		Gross unrealized losses			Fair value
U.S. treasury securities	$	—	$	—	$	(1.2	)	$	173.6	$	(1.2	)	$	173.6
Total	$	—	$	—	$	(1.2	)	$	173.6	$	(1.2	)	$	173.6

Summary of Expected Maturities of Available for Sale Securities

Expected maturities of available-for-sale securities at December 31, 2024 are as follows:

Expected maturity	Amortized cost		Fair value
One year to five years	$	24.9	$	24.7
	$	24.9	$	24.7