Annual report pursuant to Section 13 and 15(d)

Reportable Segments - Narrative (Detail)

v3.19.1
Reportable Segments - Narrative (Detail)
$ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Sep. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Mar. 31, 2017
USD ($)
Sep. 30, 2018
business_line
Dec. 31, 2018
USD ($)
business_line
segment
ft
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Segment Reporting Information [Line Items]                        
Number of business lines | business_line                 2 2    
Number of reportable segments | segment                   2    
Number of reportable subsegments | segment                   4    
Revenues $ 129,148 $ 123,395 $ 118,603 $ 109,675 $ 116,334 $ 118,308 $ 109,607 $ 98,271   $ 480,821 $ 442,520 $ 427,004
Depreciation and amortization                   $ 107,545 122,373 139,795
Consumed and replenished period                   1 year    
Corporate                        
Segment Reporting Information [Line Items]                        
Depreciation and amortization                   $ 8,400 8,700 8,300
Reimbursable revenue                        
Segment Reporting Information [Line Items]                        
Revenues                   54,600 57,800 69,300
Exxon Neftegas Limited (ENL) | Reimbursable revenue                        
Segment Reporting Information [Line Items]                        
Revenues                   $ 47,200 $ 50,800 $ 67,000
Exxon Neftegas Limited (ENL) | Customer Concentration Risk | Sales Revenue, Net                        
Segment Reporting Information [Line Items]                        
Percentage of revenue from major customer                   25.70% 31.30% 38.70%
Exxon Neftegas Limited (ENL) | Customer Concentration Risk | Sales Revenue, Net of Reimbursable Revenues                        
Segment Reporting Information [Line Items]                        
Percentage of revenue from major customer                   17.90% 22.70% 27.50%
International & Alaska Drilling | Exxon Neftegas Limited (ENL) | Customer Concentration Risk | Sales Revenue, Net                        
Segment Reporting Information [Line Items]                        
Percentage of revenue from major customer                   58.00% 55.90% 57.50%
International & Alaska Drilling | Exxon Neftegas Limited (ENL) | Customer Concentration Risk | Sales Revenue, Net of Reimbursable Revenues                        
Segment Reporting Information [Line Items]                        
Percentage of revenue from major customer                   48.00% 46.10% 45.00%
Minimum | U.S. (Lower 48) Drilling                        
Segment Reporting Information [Line Items]                        
Underwater drilling depth (in feet) | ft                   6    
Contract term                   20 days    
Maximum | U.S. (Lower 48) Drilling                        
Segment Reporting Information [Line Items]                        
Underwater drilling depth (in feet) | ft                   12    
Contract term                   180 days