Commitments and Contingencies (Details)			1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 01, 2021 USD ($)	Apr. 14, 2020 USD ($) business_day	May 12, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)
Guarantor Obligations [Line Items]
Professional, general and workers' compensation insurance reserve				$ 21,800,000		$ 21,800,000			$ 19,400,000
Expected insurance recoveries				12,100,000		12,100,000			12,100,000
Payment under settlement agreement		$ 40,000,000.0	$ 1,800,000
Interest rate		2.75%
Approved paid claims			$ 7,500,000
Payment schedule, initial payment, number of business days post Settlement Agreement date | business_day		20
Litigation settlement				0	$ 0	$ 1,200,000	$ 0	$ 46,000,000.0
Projected tax savings period						5 years
Federal effective tax rate						24.00%
Long-term tax receivable agreement liability				60,100,000		$ 60,100,000			60,100,000
Net long-term tax receivable agreement liability				52,500,000		52,500,000			48,700,000
Current portion of tax liability				$ 16,900,000		$ 16,900,000			$ 16,900,000
Federal Funds Rate
Guarantor Obligations [Line Items]
Debt instrument, basis spread on variable rate						3.00%
Collaborative tax agreement, basis spread on variable rate						3.00%
LIBOR | Materially More Restrictive
Guarantor Obligations [Line Items]
Debt instrument, basis spread on variable rate						5.00%
LIBOR | Not Materially More Restrictive
Guarantor Obligations [Line Items]
Debt instrument, basis spread on variable rate						3.00%
Tampa Pain
Guarantor Obligations [Line Items]
Corporate integrity agreement term		5 years
Logan Labs
Guarantor Obligations [Line Items]
Corporate integrity agreement term		3 years
Forecast
Guarantor Obligations [Line Items]
Payment under settlement agreement	$ 30,700,000