Acquisitions and Disposals - Additional Information (Details) $ in Millions	4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($)	Aug. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) surgical_facility	Dec. 31, 2018 USD ($) surgical_facility	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) surgical_hospital	Dec. 31, 2018 USD ($) surgery_center
Business Acquisition [Line Items]
Total cash consideration, net of cash acquired	$ 29.2	$ 725.9	$ 13.8		$ 106.8
Goodwill	3,346.8		3,402.4	$ 3,382.8	3,382.8	$ 3,382.8	$ 3,382.8
Gain (loss) on disposals and deconsolidation, net	$ 0.0	$ (1.7)	$ 4.4		(31.8)
Disposal Group One
Business Acquisition [Line Items]
Number of interests sold						2	4
Net cash proceeds from sale of interests					18.7
Net pre-tax gain (loss) on sale of interests					21.2
Surgical Facility
Business Acquisition [Line Items]
Number of business entities acquired | surgical_facility			1	5
Surgical Facility
Business Acquisition [Line Items]
Cash consideration			$ 26.7		106.4
Total cash consideration, net of cash acquired			20.1		105.6
Goodwill			22.6	$ 155.9	$ 155.9	$ 155.9	$ 155.9
Surgical facility services | Total Acquisitions In 2018
Business Acquisition [Line Items]
Goodwill			14.1
Ancillary services | Total Acquisitions In 2018
Business Acquisition [Line Items]
Goodwill			8.5
Disposed of by Sale
Business Acquisition [Line Items]
Gain (loss) on disposals and deconsolidation, net			$ 10.9