Annual report pursuant to Section 13 and 15(d)

Notes Payable to Former Stockholders - Schedule of Accounts Payable and Other Liabilities Pertaining to Notes (Detail)

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Notes Payable to Former Stockholders - Schedule of Accounts Payable and Other Liabilities Pertaining to Notes (Detail) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Accounts Payable and Accrued Expenses [Member]    
Accounts Payable And Accrued Expenses [Line Items]    
Accrued interest $ 271 $ 305