Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v3.8.0.1
Summary of Significant Accounting Policies - Additional Information (Detail)
$ in Millions
3 Months Ended
Mar. 31, 2018
USD ($)
segment
business_line
Mar. 31, 2017
USD ($)
Dec. 31, 2017
USD ($)
Revenue, Major Customer [Line Items]      
Number of business lines | business_line 2    
Percentage accounted for under the equity method 50.00%    
Deposits in domestic bank $ 76.5   $ 97.6
Uninsured deposits in foreign banks 45.1   $ 45.6
Exxon Neftegas Limited      
Revenue, Major Customer [Line Items]      
Reimbursement revenue $ 12.1 $ 13.0  
Customer Concentration Risk | Sales Revenue, Net | Exxon Neftegas Limited      
Revenue, Major Customer [Line Items]      
Percentage of revenue from major customer 28.60% 34.90%  
Customer Concentration Risk | Sales Revenue, Net Of Reimbursable Revenues | Exxon Neftegas Limited      
Revenue, Major Customer [Line Items]      
Percentage of revenue from major customer 20.10% 25.70%  
Minimum      
Revenue, Major Customer [Line Items]      
Estimated Useful Life (Years) 3 years    
Maximum      
Revenue, Major Customer [Line Items]      
Estimated Useful Life (Years) 6 years    
U.S. (Lower 48) Drilling      
Revenue, Major Customer [Line Items]      
Number of business lines | business_line 2    
Number of reportable segments | segment 2    
International & Alaska Drilling      
Revenue, Major Customer [Line Items]      
Number of reportable segments | segment 2    
International & Alaska Drilling | Customer Concentration Risk | Sales Revenue, Net | Exxon Neftegas Limited      
Revenue, Major Customer [Line Items]      
Percentage of revenue from major customer 55.90% 54.30%  
International & Alaska Drilling | Customer Concentration Risk | Sales Revenue, Net Of Reimbursable Revenues | Exxon Neftegas Limited      
Revenue, Major Customer [Line Items]      
Percentage of revenue from major customer 45.90% 44.40%