Annual report pursuant to Section 13 and 15(d)

Concentrations of Credit Risk - Additional Information (Detail)

v3.8.0.1
Concentrations of Credit Risk - Additional Information (Detail)
$ in Thousands
12 Months Ended
Dec. 31, 2016
USD ($)
Customer
Dec. 31, 2015
Customer
Dec. 31, 2017
USD ($)
Customer
Dec. 31, 2016
USD ($)
Customer
Dec. 31, 2015
Customer
Concentration Risk [Line Items]          
Trade accounts receivable | $ $ 110   $ 0 $ 110  
Trade Accounts Receivable [Member]          
Concentration Risk [Line Items]          
Concentration risk, number of customers 1 2      
Revenue Concentration [Member]          
Concentration Risk [Line Items]          
Concentration risk, number of customers     3 4 3
Customer 1 [Member] | Trade Accounts Receivable [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage 100.00% 50.00%      
Customer 1 [Member] | Revenue Concentration [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage     51.00% 33.00% 38.00%
Customer 2 [Member] | Trade Accounts Receivable [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage   50.00%      
Customer 2 [Member] | Revenue Concentration [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage     40.60% 28.00% 26.00%
Customer 3 [Member] | Revenue Concentration [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage     6.70% 19.00% 20.00%
Customer 4 [Member] | Revenue Concentration [Member] | Customer Concentration Risk [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage       16.00%