Accounts Receivable - Additional Information (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Customer One [Member]
Accounts Notes And Loans Receivable [Line Items]
Customer account balance	$ 3,197,000	$ 2,079,000
Customer One [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Accounts Notes And Loans Receivable [Line Items]
Percentage of Accounts receivable	21.00%	20.00%
Customer Two [Member]
Accounts Notes And Loans Receivable [Line Items]
Customer account balance	$ 2,203,000	$ 2,007,000
Customer Two [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Accounts Notes And Loans Receivable [Line Items]
Percentage of Accounts receivable	14.00%	20.00%
Customer Three [Member]
Accounts Notes And Loans Receivable [Line Items]
Customer account balance	$ 1,994,000	$ 1,319,000
Customer Three [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Accounts Notes And Loans Receivable [Line Items]
Percentage of Accounts receivable	13.00%	13.00%
Customer Four [Member]
Accounts Notes And Loans Receivable [Line Items]
Customer account balance	$ 1,589,000
Customer Four [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Accounts Notes And Loans Receivable [Line Items]
Percentage of Accounts receivable	10.00%
Minimum [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Accounts Notes And Loans Receivable [Line Items]
Percentage of Accounts receivable	10.00%	10.00%