Quarterly report pursuant to Section 13 or 15(d)

Nature of Operations and Summary of Significant Accounting Policies - Clinics in Operation Under Franchise Agreements or Company-owned or Managed (Details)

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Nature of Operations and Summary of Significant Accounting Policies - Clinics in Operation Under Franchise Agreements or Company-owned or Managed (Details) - clinic
 3 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Product Information, Franchised Clinics, Company-Owned Or Managed Clinics, Activity [Roll Forward]    
Clinics in operation at the end of the period 736 592
Clinic licenses sold but not yet developed 239 223
Executed letters of intent for future clinic licenses 39 37
Franchised Clinics    
Product Information, Franchised Clinics, Company-Owned Or Managed Clinics, Activity [Roll Forward]    
Clinics open at beginning of period 610 515
Opened during the period 27 12
Sold during the period 0 0
Closed during the period (1) 0
Clinics in operation at the end of the period 636 527
Company-Owned or Managed Clinics    
Product Information, Franchised Clinics, Company-Owned Or Managed Clinics, Activity [Roll Forward]    
Clinics open at beginning of period 96 64
Opened during the period 4 1
Acquired during the period 0 0
Closed during the period 0 0
Clinics in operation at the end of the period 100 65