Organization and Summary of Accounting Policies - Schedule of Revenues by Sources (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,860.1	$ 1,831.4	$ 1,771.5
Patient service revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,836.1	$ 1,803.1	$ 1,737.0
Patient service revenues \| Customer \| Revenue
Disaggregation of Revenue [Line Items]
Revenue by service type as a percentage of total revenues	100.00%	100.00%	100.00%
Private insurance
Disaggregation of Revenue [Line Items]
Total revenues	$ 989.9	$ 970.5	$ 948.9
Private insurance \| Customer \| Revenue
Disaggregation of Revenue [Line Items]
Revenue by service type as a percentage of total revenues	53.90%	53.80%	54.60%
Government
Disaggregation of Revenue [Line Items]
Total revenues	$ 708.5	$ 701.9	$ 653.3
Government \| Customer \| Revenue
Disaggregation of Revenue [Line Items]
Revenue by service type as a percentage of total revenues	38.60%	38.90%	37.60%
Self-pay
Disaggregation of Revenue [Line Items]
Total revenues	$ 58.5	$ 46.1	$ 50.0
Self-pay \| Customer \| Revenue
Disaggregation of Revenue [Line Items]
Revenue by service type as a percentage of total revenues	3.20%	2.60%	2.90%
Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 79.2	$ 84.6	$ 84.8
Other \| Customer \| Revenue
Disaggregation of Revenue [Line Items]
Revenue by service type as a percentage of total revenues	4.30%	4.70%	4.90%
Optical Services
Disaggregation of Revenue [Line Items]
Total revenues	$ 3.0	$ 3.8	$ 9.5
Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 21.0	$ 24.5	$ 25.0