Annual report pursuant to Section 13 and 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
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Product Information, Franchised Clinics, Company-Owned Or Managed Clinics, Activity [Roll Forward]    
Clinics open at beginning of period 442  
Clinics in operation at the end of the period 513 442
Clinic licenses sold but not yet developed 170 136
Executed letters of intent for future clinic licenses 34 19
Franchised Units    
Product Information, Franchised Clinics, Company-Owned Or Managed Clinics, Activity [Roll Forward]    
Clinics open at beginning of period 394 352
Opened or Purchased during the period 71 47
Acquired or sold during the period (8) (1)
Closed during the period (4) (4)
Clinics in operation at the end of the period 453 394
Opened during the period 71 47
Acquired during the period 8 1
Closed or Sold during the period (4) (4)
Entity Operated Units    
Product Information, Franchised Clinics, Company-Owned Or Managed Clinics, Activity [Roll Forward]    
Clinics open at beginning of period 48 47
Opened or Purchased during the period 5 0
Acquired or sold during the period (8) (1)
Closed during the period (1) 0
Clinics in operation at the end of the period 60 48
Opened during the period 5 0
Acquired during the period 8 1
Closed or Sold during the period (1) 0