Annual report pursuant to Section 13 and 15(d)

Subsequent Events (Details)

v3.8.0.1
Subsequent Events (Details)
$ in Thousands
3 Months Ended 12 Months Ended
Jan. 01, 2018
USD ($)
bbl
Dec. 31, 2017
USD ($)
Sep. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Sep. 30, 2016
USD ($)
Jun. 30, 2016
USD ($)
Mar. 31, 2016
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Subsequent Event [Line Items]                        
Oil and natural gas sales   $ 17,156 $ 18,178 $ 20,425 $ 21,266 $ 15,326 $ 14,635 $ 18,847 $ 10,976 $ 77,025 $ 59,784 $ 80,445
Subsequent Event [Member]                        
Subsequent Event [Line Items]                        
Oil and natural gas sales $ 6,500                      
Net volume delivered (barrels) | bbl 95,525                      
Lifting price increase 7.10%                      
Impact on revenue from lifting price increase $ 500