Related Party Transactions - Narrative (Details) - USD ($)
1 Months Ended 12 Months Ended
Aug. 24, 2017
Jul. 31, 2017
Apr. 30, 2017
Oct. 31, 2016
Dec. 31, 2018
Dec. 31, 2017
Aug. 31, 2017
Jan. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Aug. 31, 2015
Related Party Transaction [Line Items]                      
Payments for repurchase of common stock         $ 0 $ 4,507,000          
Grants in period (in shares)         810,628            
Accounts payable due to related parties           0          
Affiliated Entity                      
Related Party Transaction [Line Items]                      
Revenue from related parties         $ 40,000 300,000          
Number of shares authorized to be repurchased                   813,140  
Authorized amount                   $ 3,700,000  
Payments for repurchase of common stock   $ 2,800,000 $ 1,700,000 $ 2,000,000              
Stock repurchased during period (in shares)   406,570   440,040              
Accounts payable due to related parties         0            
Immediate Family Member of Management or Principal Owner                      
Related Party Transaction [Line Items]                      
Revenue from related parties         900,000 600,000          
Accounts receivable         $ 200,000 100,000          
Grants in period (in shares)         20,580            
Vesting period         4 years            
Cash reimbursement per day for services         $ 4,500            
Purchases from related party         90,000 120,000          
Executive Officer                      
Related Party Transaction [Line Items]                      
Principal balance outstanding                 $ 200,000    
Convertible Debt | Related Party Convertible Notes Payable | Affiliated Entity                      
Related Party Transaction [Line Items]                      
Conversion of related party convertible notes payable into ordinary shares 5,869,417                    
Principal balance outstanding         0 0          
Notes Payable | Affiliated Entity                      
Related Party Transaction [Line Items]                      
Principal balance               $ 1,200,000      
Notes Payable | Seven Percent Notes Payable | Affiliated Entity                      
Related Party Transaction [Line Items]                      
Principal balance outstanding         $ 0 4,218,000         $ 4,300,000
Principal balance                     $ 4,200,000
Line of Credit | Madryn Credit Agreement                      
Related Party Transaction [Line Items]                      
Principal balance outstanding           $ 40,000,000          
Maximum borrowing capacity             $ 55,000,000.0        
CPH TU, L.P. | Convertible Debt | Related Party Convertible Notes Payable | Affiliated Entity                      
Related Party Transaction [Line Items]                      
Related party ownership percentage of company         37.10%            
Madryn                      
Related Party Transaction [Line Items]                      
Related party ownership percentage of company         3.60%