v3.8.0.1
Commitments and Contingencies - Long-Term Debt and PO Commitments (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Jun. 17, 2016
Estimated Litigation Liability $ 0    
Recorded Unconditional Purchase Obligation Due in Next Twelve Months 71,700,000    
Property and Equipment, Gross 200,400,000 $ 156,600,000  
Financing lease obligations $ 6,700,000 $ 6,700,000  
Purchase commitments with vendors total maximum term, in years 1 year    
Line of Credit [Member]      
Long-term Line of Credit     $ 200,000,000
Debt Issuance Costs, Line of Credit Arrangements, Gross     $ 700,000