Revenue (Tables)

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

Revenue from External Customers by Geographic Areas [Table Text Block]

	Years ended December 31,
Total revenue:	2022		2021		2020
United States	$	7,031.0	$	6,360.2	$	5,751.5
International:
United Kingdom	902.7		880.5		742.9
Continental Europe	867.5		892.8		763.5
Asia Pacific	918.5		970.1		879.5
Latin America	454.9		430.3		349.7
Other	753.2		706.8		573.9
Total International	3,896.8		3,880.5		3,309.5
Total Consolidated	$	10,927.8	$	10,240.7	$	9,061.0

	Years ended December 31,
Revenue before billable expenses:	2022		2021		2020
United States	$	6,157.7	$	5,763.1	$	5,211.4
International:
United Kingdom	742.2		781.5		664.3
Continental Europe	764.6		799.7		683.6
Asia Pacific	772.7		791.4		710.5
Latin America	423.6		396.4		323.4
Other	588.6		575.8		471.3
Total International	3,291.7		3,344.8		2,853.1
Total Consolidated	$	9,449.4	$	9,107.9	$	8,064.5

MD&E	Years ended December 31,
Total revenue:	2022		2021		2020
United States	$	2,547.8	$	2,432.6	$	2,196.6
International	1,648.9		1,629.1		1,323.8
Total MD&E	$	4,196.7	$	4,061.7	$	3,520.4
Revenue before billable expenses:
United States	$	2,512.1	$	2,403.6	$	2,168.9
International	1,599.4		1,570.0		1,282.3
Total MD&E	$	4,111.5	$	3,973.6	$	3,451.2

IA&C	Years ended December 31,
Total revenue:	2022		2021		2020
United States	$	2,768.3	$	2,555.4	$	2,323.0
International	1,557.2		1,621.3		1,401.6
Total IA&C	$	4,325.5	$	4,176.7	$	3,724.6
Revenue before billable expenses:
United States	$	2,662.5	$	2,454.4	$	2,230.3
International	1,289.2		1,369.4		1,197.2
Total IA&C	$	3,951.7	$	3,823.8	$	3,427.5

SC&E	Years ended December 31,
Total revenue:	2022		2021		2020
United States	$	1,714.9	$	1,372.2	$	1,231.9
International	690.7		630.1		584.1
Total SC&E	$	2,405.6	$	2,002.3	$	1,816.0
Revenue before billable expenses:
United States	$	983.1	$	905.1	$	812.2
International	403.1		405.4		373.6
Total SC&E	$	1,386.2	$	1,310.5	$	1,185.8

Contract with Customer, Asset and Liability [Table Text Block]

Contract Balances

The following table provides information about receivables, contract assets and contract liabilities from contracts with customers.

	December 31, 2022		December 31, 2021
Accounts receivable, net of allowance of $48.6 and $68.5, respectively	$	5,316.0	$	5,177.7
Accounts receivable, billable to clients	2,023.0		2,347.2
Contract assets	67.4		62.3
Contract liabilities (deferred revenue)	680.0		688.5