Accrued Expenses and Other Current Liabilities and Other Liabilities - Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Patient prepayments, deposits, and refunds payable	$ 25,075	$ 27,195
Accrued sales taxes and other taxes	9,456	9,863
Insurance and self-insurance accruals	7,518	7,651
Derivative liability	7,461	7,686
Accrued professional fees	1,177	1,016
Accrued interest payable	581	440
Other current liabilities	7,904	9,010
Total	$ 59,172	$ 62,861