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Commitments and Contingencies - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Loss Contingencies [Line Items]    
Potential liability related to asset purchase agreement $ 4,300,000  
Medical And Hospitalization Insurance Program    
Loss Contingencies [Line Items]    
Minimum insurance premium 600,000 $ 900,000
Insurance reserves   $ 130,000
Maximum | Medical And Hospitalization Insurance Program    
Loss Contingencies [Line Items]    
Liable for all claims per insured annual amount 70,000  
Liable for all claims per insured aggregate amount $ 1,700,000