Quarterly report pursuant to Section 13 or 15(d)

Concentrations of Credit Risk - Additional Information (Detail)

v3.7.0.1
Concentrations of Credit Risk - Additional Information (Detail)
$ in Thousands
3 Months Ended 6 Months Ended
Dec. 31, 2016
USD ($)
Customer
Jun. 30, 2017
USD ($)
Customer
Jun. 30, 2016
Customer
Jun. 30, 2017
USD ($)
Customer
Jun. 30, 2016
Customer
Concentration Risk [Line Items]          
Trade accounts receivable | $ $ 110 $ 0   $ 0  
Trade Accounts Receivable [Member]          
Concentration Risk [Line Items]          
Concentration risk, number of customers 1        
Revenue Concentration [Member]          
Concentration Risk [Line Items]          
Concentration risk, number of customers   2 4 2 4
Customer 1 [Member] | Trade Accounts Receivable [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage 100.00%        
Customer 1 [Member] | Revenue Concentration [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage   82.70% 31.60% 72.30% 31.60%
Customer 2 [Member] | Revenue Concentration [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage   12.40% 24.90% 20.00% 24.90%
Customer 3 [Member] | Revenue Concentration [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage     24.40%   24.40%
Customer 4 [Member] | Revenue Concentration [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage     14.40%   14.40%