Quarterly report pursuant to Section 13 or 15(d)

Selected Balance Sheet Data - Schedule of Other Assets (Parenthetical) (Detail)

v3.10.0.1
Selected Balance Sheet Data - Schedule of Other Assets (Parenthetical) (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Other Assets [Line Items]          
Allowance of doubtful accounts $ 474   $ 474   $ 494
Provision for bad debt expense 81 $ 87 52 $ 33  
Write-off receivables $ 17 $ 4 $ 72 $ 14  
Minimum [Member]          
Other Assets [Line Items]          
Notes receivable due period     1 year    
Maximum [Member]          
Other Assets [Line Items]          
Notes receivable due period     5 years