Segment Reporting - Assets and Cash Purchases of Property and Equipment by Operating Segment (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total assets	$ 5,312.9		$ 5,018.9
Total cash purchases of property and equipment	27.8	$ 50.2
Operating Segments | Surgical Facility Services
Segment Reporting Information [Line Items]
Total assets	4,745.0		4,580.4
Total cash purchases of property and equipment	24.1	42.8
Operating Segments | Ancillary Services
Segment Reporting Information [Line Items]
Total assets	34.8		69.6
Total cash purchases of property and equipment	0.3	0.5
Operating Segments | Optical services revenues
Segment Reporting Information [Line Items]
Total assets	14.2		17.7
All other
Segment Reporting Information [Line Items]
Total assets	518.9		$ 351.2
Total cash purchases of property and equipment	$ 3.4	$ 6.9