Acquisitions and Disposals - Acquisitions (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020 USD ($) surgery_center	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Business Acquisition [Line Items]
Payments for acquisitions, net of cash acquired	$ 14.2	$ 13.8
Net assets acquired:
Goodwill	3,344.6		$ 3,402.4
Surgical Facilities
Business Acquisition [Line Items]
Payments for acquisitions, net of cash acquired	14.2
Noncash consideration	3.2
Total consideration	18.6
Fair value of non-controlling interests	6.7
Aggregate acquisition date fair value	25.3
Net assets acquired:
Current assets	1.9
Property and equipment	5.8
Goodwill	23.8
Right-of-use operating lease assets	10.7
Current liabilities	(2.0)
Long-term debt, less current maturities	(4.6)
Right-of-use operating lease liabilities	(10.3)
Aggregate acquisition date fair value	$ 25.3
Surgical Facilities, New Market
Business Acquisition [Line Items]
Number of facilities acquired | surgery_center	1
Surgical Facilities, Existing Markets
Business Acquisition [Line Items]
Number of facilities acquired | surgery_center	4