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Property and Equipment, Net - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property, Plant and Equipment [Line Items]      
Depreciation expense $ 17.3 $ 13.4 $ 9.1
Lease expiration year, earliest 2019    
Lease expiration year, latest 2025    
Expected rental income, during 2018 $ 1.5    
Expected rental income, during 2019 1.4    
Expected rental income, during 2020 1.4    
Expected rental income, during 2021 1.4    
Expected rental income, during 2022 1.5    
Expected rental income, thereafter 4.3    
Rental income from third party tenants in 2016, 2015, and 2014 1.5 1.7 $ 0.9
Latham, New York      
Property, Plant and Equipment [Line Items]      
Payment to acquire building 2.9    
Payment for construction to expand building 2.1    
Yarmouth, Maine      
Property, Plant and Equipment [Line Items]      
Payment to acquire building   9.7  
Payment for construction to expand building $ 19.4 $ 8.0