Variable Interest Entities - Carrying Amounts and Classification of Consolidated VIEs (Details) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents		$ 54.8	$ 224.0	$ 94.8	$ 69.2
Accounts receivable		680.3	572.8
Total current assets		921.4	948.6
Property and equipment, net		2,601.6	2,206.6
Operating lease right-of-use assets		242.0	245.7
Goodwill		2,427.9	2,318.7	$ 2,305.2	$ 2,100.8
Intangible assets, net		417.5	431.3
Other long-term assets		254.5	295.0
Total assets	[1]	6,864.9	6,445.9
Current liabilities:
Current portion of long-term debt		42.8	38.3
Current operating lease liabilities		38.4	44.8
Accounts payable		137.6	115.0
Accrued payroll		265.8	253.8
Other current liabilities		219.7	218.3
Total current liabilities		748.8	717.3
Long-term debt, net of current portion		3,243.9	3,250.6
Long-term operating lease liabilities		213.1	209.6
Other long-term liabilities		49.4	93.8
Total liabilities		4,465.7	4,444.3
Variable Interest Entity, Primary Beneficiary
Current assets:
Cash and cash equivalents		0.0	0.1
Accounts receivable		36.3	33.1
Other current assets		7.7	8.6
Total current assets		44.0	41.8
Property and equipment, net		116.3	121.1
Operating lease right-of-use assets		3.2	4.7
Goodwill		28.3	19.2
Intangible assets, net		3.3	3.3
Deferred income tax assets		0.6	0.5
Other long-term assets		30.5	30.6
Total assets		226.2	221.2
Current liabilities:
Current portion of long-term debt		1.0	0.9
Current operating lease liabilities		1.5	1.5
Accounts payable		5.9	6.1
Accrued payroll		10.2	11.3
Other current liabilities		9.2	11.7
Total current liabilities		27.8	31.5
Long-term debt, net of current portion		8.6	9.6
Long-term operating lease liabilities		1.8	3.3
Other long-term liabilities		0.0	2.4
Total liabilities		$ 38.2	$ 46.8

[1] Our consolidated assets as of December 31, 2021 and December 31, 2020 include total assets of variable interest entities of $226.2 million and $221.2 million, respectively, which cannot be used by us to settle the obligations of other entities. Our consolidated liabilities as of December 31, 2021 and December 31, 2020 include total liabilities of the variable interest entities of $38.2 million and $46.8 million, respectively. See Note 3, Variable Interest Entities.