Revenue Contract Balances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Accounts receivable, net of allowance of $46.4 and $48.6, respectively	$ 5,768.8	$ 5,316.0
Accounts receivable, billable to clients	2,229.2	2,023.0
Contract with Customer, Asset, after Allowance for Credit Loss	68.6	67.4
Contract liabilities	684.7	680.0
Revenue, remaining performance obligation, amount	716.5
Net revenue	$ 9,400.6	$ 9,449.4