Quarterly report pursuant to Section 13 or 15(d)

Notes Payable to Former Stockholders - Schedule of Interest Expense Pertaining to Notes (Detail)

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Notes Payable to Former Stockholders - Schedule of Interest Expense Pertaining to Notes (Detail) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Interest Expense [Line Items]    
Interest expense $ 360 $ 382
Notes Payable to Former Stockholders [Member]    
Interest Expense [Line Items]    
Interest expense $ 109 $ 122