Segment Data - Schedule of Segment Data (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues from services	$ 5,054.9	$ 4,584.8	$ 3,742.2	$ 4,619.1	$ 5,196.6	$ 5,248.9	$ 5,373.1	$ 5,044.9	$ 18,001.0	$ 20,863.5	$ 21,991.2
Franchise fees
Segment Reporting Information [Line Items]
Revenues from services									14.1	18.4	24.1
Americas
Segment Reporting Information [Line Items]
Revenues from services									3,792.4	4,278.6	4,258.9
Americas | United States
Segment Reporting Information [Line Items]
Revenues from services									2,327.2	2,590.6	2,608.9
Americas | United States | Franchise fees
Segment Reporting Information [Line Items]
Revenues from services									$ 12.6	$ 15.6	$ 16.1