Quarterly report pursuant to Section 13 or 15(d)

Organization And Accounting Policies (Detail)

v3.5.0.2
Organization And Accounting Policies (Detail)
 3 Months Ended 9 Months Ended
Sep. 30, 2016
USD ($)
item
Dec. 31, 2015
USD ($)
Sep. 30, 2015
USD ($)
Sep. 30, 2016
USD ($)
item
Sep. 30, 2015
USD ($)
Error Corrections and Prior Period Adjustments Restatement [Line Items]          
Value Added Tax Reimbursement Monthly Payment       $ 200,000  
Allowance for Doubtful Accounts Receivable, Period Increase (Decrease) $ 100,000   $ 2,800,000 $ 600,000 $ 2,800,000
Number Of Value Added Tax Reimbursement Payments | item 36        
United States [Member]          
Error Corrections and Prior Period Adjustments Restatement [Line Items]          
Number of unconventional wells | item 2     2  
Overstated [Member] | Angola [Member]          
Error Corrections and Prior Period Adjustments Restatement [Line Items]          
Allowance For Doubtful Accounts Receivable   $ 7,600,000      
Group 42-BLR Group [Member]          
Error Corrections and Prior Period Adjustments Restatement [Line Items]          
Legal expense   $ 350,000