Revenue Major Geographical Area (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net revenue	$ 9,107.9	$ 8,064.5	$ 8,625.1
Total revenue	10,240.7	9,061.0	10,221.3
United States
Net revenue	5,763.1	5,211.4	5,386.1
Total revenue	6,360.2	5,751.5	6,368.7
Total International
Net revenue	3,344.8	2,853.1	3,239.0
Total revenue	3,880.5	3,309.5	3,852.6
United Kingdom
Net revenue	781.5	664.3	727.0
Total revenue	880.5	742.9	871.8
Continental Europe
Net revenue	799.7	683.6	742.4
Total revenue	892.8	763.5	842.9
Asia Pacific
Net revenue	791.4	710.5	858.3
Total revenue	970.1	879.5	1,102.3
Latin America
Net revenue	396.4	323.4	389.9
Total revenue	430.3	349.7	431.6
Other
Net revenue	575.8	471.3	521.4
Total revenue	706.8	573.9	604.0
IAN
Net revenue	7,839.8	6,921.4	7,328.8
Total revenue	8,419.4	7,410.1	7,992.0
IAN | United States
Net revenue	4,912.8	4,451.7	4,538.1
Total revenue	5,147.8	4,658.5	4,878.1
IAN | Total International
Net revenue	2,927.0	2,469.7	2,790.7
Total revenue	3,271.6	2,751.6	3,113.9
DXTRA
Net revenue	1,268.1	1,143.1	1,296.3
Total revenue	1,821.3	1,650.9	2,229.3
DXTRA | United States
Net revenue	850.3	759.7	848.0
Total revenue	1,212.4	1,093.0	1,490.6
DXTRA | Total International
Net revenue	417.8	383.4	448.3
Total revenue	$ 608.9	$ 557.9	$ 738.7