Annual report pursuant to Section 13 and 15(d)

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

v3.10.0.1
Notes Payable to Former Stockholders - Schedule of Interest Expense Pertaining to Notes (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Interest Expense [Line Items]      
Interest expense $ 1,400 $ 1,496 $ 1,533
Notes Payable to Former Stockholders [Member]      
Interest Expense [Line Items]      
Interest expense $ 404 $ 454 $ 502