Segment Data - Schedule of Segment Data (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2025		Sep. 30, 2024		Sep. 30, 2025		Sep. 30, 2024
Segment Reporting Information [Line Items]
Revenues from services	$ 4,634.4		$ 4,530.2	[1]	$ 13,244.0		$ 13,454.2	[2]
Cost of Services	3,865.5		3,748.1		11,013.1		11,122.5
Selling and Administrative Expenses	702.3		711.3		2,161.4		2,093.9
Corporate expenses	(40.9)		(30.2)		(137.1)		(113.6)
Impairment charges	0.0		0.0		(88.7)	[3]	0.0
Intangible asset amortization expense	(7.9)	[4]	(8.2)	[5]	(24.3)	[6]	(24.6)	[7]
Operating profit	66.6		70.8		69.5		237.8
Interest and other expenses, net	(13.7)		(11.6)		(41.7)		(28.7)
Earnings before income taxes	52.9		59.2		27.8		209.1
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues from services	(7.1)		(7.0)	[1]	(24.4)		(47.2)	[2]
Cost of Services	(6.3)		(4.6)		(20.3)		(44.8)
Selling and Administrative Expenses	(0.8)		(2.4)		(4.1)		(2.4)
Operating unit profit	0.0		0.0		0.0		0.0
United States | Americas
Segment Reporting Information [Line Items]
Revenues from services			697.4	[8]			2,074.8	[9]
Other Americas | Americas
Segment Reporting Information [Line Items]
Revenues from services			353.1	[8]			1,076.5	[9]
France | Southern Europe
Segment Reporting Information [Line Items]
Revenues from services			1,156.8	[8]			3,420.2	[9]
Italy | Southern Europe
Segment Reporting Information [Line Items]
Revenues from services			419.1	[8]			1,258.3	[9]
Other Southern Europe | Southern Europe
Segment Reporting Information [Line Items]
Revenues from services			519.7	[8]			1,496.4	[9]
Reportable subsegments
Segment Reporting Information [Line Items]
Revenues from services	4,634.4		4,530.2		13,244.0		13,454.2
Cost of Services	3,865.5		3,748.0		11,013.1		11,122.4
Selling and Administrative Expenses	653.5		673.0		1,911.3		1,955.8
Operating unit profit	115.4		109.2		319.6		376.0
Reportable subsegments | Americas
Segment Reporting Information [Line Items]
Revenues from services	1,098.7		1,050.5	[1]	3,215.4		3,151.3	[2]
Cost of Services	857.4		807.8		2,512.8		2,425.0
Selling and Administrative Expenses	203.4		206.6		603.1		619.0
Operating unit profit	37.9		36.1		99.5		107.3
Reportable subsegments | Southern Europe
Segment Reporting Information [Line Items]
Revenues from services	2,205.5		2,095.6	[1]	6,188.8		6,174.9	[2]
Cost of Services	1,896.8		1,790.3	[10]	5,301.6		5,268.5	[11]
Selling and Administrative Expenses	243.1		229.5	[10]	698.1		677.5	[11]
Operating unit profit	65.6		75.8	[10]	189.1		228.9	[11]
Reportable subsegments | Northern Europe
Segment Reporting Information [Line Items]
Revenues from services	816.8		828.3	[1]	2,342.0	[2]	2,535.9	[2]
Cost of Services	684.3		680.4		1,952.4		2,091.4
Selling and Administrative Expenses	147.4		173.6		431.8		472.6
Operating unit profit	(14.9)		(25.7)		(42.2)		(28.1)
Reportable subsegments | APME
Segment Reporting Information [Line Items]
Revenues from services	520.5		562.8	[1]	1,522.2		1,639.3	[2]
Cost of Services	433.3		474.1		1,266.6		1,382.3
Selling and Administrative Expenses	60.4		65.7		182.4		189.1
Operating unit profit	26.8		23.0		73.2		67.9
Reportable subsegments | Northern Europe and APME
Segment Reporting Information [Line Items]
Revenues from services	4,641.5		4,537.2	[1]	13,268.4		13,501.4	[2]
Cost of Services	3,871.8		3,752.6		11,033.4		11,167.2
Selling and Administrative Expenses	654.3		675.4		1,915.4		1,958.2
Operating unit profit	115.4		109.2		319.6		376.0
Reportable subsegments | United States | Americas
Segment Reporting Information [Line Items]
Revenues from services	690.8	[12]	697.4	[1],[13]	2,053.7	[14]	2,074.8	[2],[15]
Cost of Services	515.7	[12]	509.9	[13]	1,530.9	[14]	1,525.8	[15]
Selling and Administrative Expenses	154.5	[12]	165.2	[13]	471.2	[14]	487.3	[15]
Operating unit profit	20.6	[12]	22.3	[13]	51.6	[14]	61.7	[15]
Reportable subsegments | Other Americas | Americas
Segment Reporting Information [Line Items]
Revenues from services	407.9		353.1	[1]	1,161.7		1,076.5	[2]
Cost of Services	341.7		297.9		981.9		899.2
Selling and Administrative Expenses	48.9		41.4		131.9		131.7
Operating unit profit	17.3		13.8		47.9		45.6
Reportable subsegments | France | Southern Europe
Segment Reporting Information [Line Items]
Revenues from services	1,173.5		1,156.8	[1]	3,288.5		3,420.2	[2]
Cost of Services	1,010.5		987.5	[10]	2,818.4		2,922.6	[11]
Selling and Administrative Expenses	132.4		128.1	[10]	386.2		383.9	[11]
Operating unit profit	30.6		41.2	[10]	83.9		113.7	[11]
Reportable subsegments | Italy | Southern Europe
Segment Reporting Information [Line Items]
Revenues from services	462.5		419.1	[1]	1,336.2		1,258.3	[2]
Cost of Services	390.6		350.2	[10]	1,124.7		1,046.7	[11]
Selling and Administrative Expenses	45.3		41.5	[10]	128.5		122.8	[11]
Operating unit profit	26.6		27.4	[10]	83.0		88.8	[11]
Reportable subsegments | Other Southern Europe | Southern Europe
Segment Reporting Information [Line Items]
Revenues from services	569.5		519.7	[1]	1,564.1		1,496.4	[2]
Cost of Services	495.7		452.6	[10]	1,358.5		1,299.2	[11]
Selling and Administrative Expenses	65.4		59.9	[10]	183.4		170.8	[11]
Operating unit profit	$ 8.4		$ 7.2	[10]	$ 22.2		$ 26.4	[11]

[1] Effective January 1, 2025, our segment reporting was realigned to include our Morocco business within Other Southern Europe. Accordingly, France is now adjusted to exclude Morocco. All previously reported results have been recast to conform to the current year presentation.

[2] Effective January 1, 2025, our segment reporting was realigned to include our Morocco business within Other Southern Europe. Accordingly, France is now adjusted to exclude Morocco. All previously reported results have been recast to conform to the current year presentation.

[3] Impairment charges for the nine months ended September 30, 2025 consist of a goodwill impairment related to our investments in Switzerland and the United Kingdom and an impairment of an indefinite lived intangible asset in our Switzerland business.

[4] Intangible asset amortization related to acquisitions is excluded from operating costs within the reportable segments and corporate expenses and shown separately.

[5] Intangible asset amortization related to acquisitions is excluded from operating costs within the reportable segments and corporate expenses and shown separately.

[6] Intangible asset amortization related to acquisitions is excluded from operating costs within the reportable segments and corporate expenses and shown separately.

[7] Intangible asset amortization related to acquisitions is excluded from operating costs within the reportable segments and corporate expenses and shown separately.

[8] Effective January 1, 2025, our segment reporting was realigned to include our Morocco business within Other Southern Europe. Accordingly, France is now adjusted to exclude Morocco. All previously reported results have been recast to conform to the current year presentation.

[9] Effective January 1, 2025, our segment reporting was realigned to include our Morocco business within Other Southern Europe. Accordingly, France is now adjusted to exclude Morocco. All previously reported results have been recast to conform to the current year presentation.

[10] Effective January 1, 2025, our segment reporting was realigned to include our Morocco business within Other Southern Europe. Accordingly, France is now adjusted to exclude Morocco. All previously reported results have been recast to conform to the current year presentation.

[11] Effective January 1, 2025, our segment reporting was realigned to include our Morocco business within Other Southern Europe. Accordingly, France is now adjusted to exclude Morocco. All previously reported results have been recast to conform to the current year presentation.

[12] The United States revenues above represent revenues from our company-owned branches and franchise fees received from our franchise operations, which were $2.7 for the three months ended September 30, 2025.

[13] The United States revenues above represent revenues from our company-owned branches and franchise fees received from our franchise operations, which were $2.5 for the three months ended September 30, 2024.

[14] The United States revenues above represent revenues from our company-owned branches and franchise fees received from our franchise operations, which were $7.5 for the nine months ended September 30, 2025.

[15] The United States revenues above represent revenues from our company-owned branches and franchise fees received from our franchise operations, which were $8.1 for the nine months ended September 30, 2024.