Annual report pursuant to Section 13 and 15(d)

Commitments - Additional Information (Details)

v3.6.0.2
Commitments - Additional Information (Details) - USD ($)
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Commitments [Line Items]      
Minimum future lease payments due under noncancelable operating leases, 2017 $ 1,600,000    
Minimum future lease payments due under noncancelable operating leases, 2018 1,700,000    
Minimum future lease payments due under noncancelable operating leases, 2019 1,800,000    
Minimum future lease payments due under noncancelable operating leases, 2020 1,800,000    
Minimum future lease payments due under noncancelable operating leases, thereafter 3,700,000    
Total rent expense 3,200,000 $ 3,300,000 $ 3,200,000
Security amount requirement 75,000,000    
Escrow deposit 1,900,000    
Additional security requirements for 2017 83,000,000    
Additional security requirements for 2018 88,000,000    
Additional security requirements for 2023 103,000,000    
Annual increment in threshold 3,000,000    
Collateral deposits 16,900,000    
Expenses related to surety bonds 4,300,000 $ 5,500,000 $ 4,100,000
ARO Projects      
Commitments [Line Items]      
Minimum future lease payments due under noncancelable operating leases, 2016 2,900,000    
Drilling Rig Commitments      
Commitments [Line Items]      
Minimum future lease payments due under noncancelable operating leases, 2016 7,400,000    
Helix Well Containment Group      
Commitments [Line Items]      
Future estimated costs, 2017 1,700,000    
Future estimated costs, 2018 1,700,000    
Surety Bonds      
Commitments [Line Items]      
Future estimated costs, 2017 6,100,000    
Future estimated costs, 2018 5,900,000    
Future estimated costs, 2019 5,200,000    
Future estimated costs, 2020 5,000,000    
Future estimated costs, thereafter 38,600,000    
Other commitment      
Commitments [Line Items]      
Security requirement minimum 64,000,000    
Security requirement maximum $ 94,000,000