Quarterly report pursuant to Section 13 or 15(d)

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

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Selected Balance Sheet Data - Schedule of Other Assets (Parenthetical) (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Dec. 31, 2014
Other Assets [Line Items]          
Allowance of doubtful accounts $ 237,000   $ 237,000   $ 193,000
Provision for bad debt expense 58,000 $ 31,000 79,000 $ 42,000  
Write-off receivables $ 29,000 $ 46,000 $ 35,000 $ 87,000  
Minimum [Member]          
Other Assets [Line Items]          
Notes receivable due period     1 year    
Maximum [Member]          
Other Assets [Line Items]          
Notes receivable due period     5 years