Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Natural Gas Properties (unaudited) (Capitalized Costs Relating to Oil and Natural Gas Activities - Additional Information) (Details)

v3.8.0.1
Supplemental Information on Oil and Natural Gas Properties (unaudited) (Capitalized Costs Relating to Oil and Natural Gas Activities - Additional Information) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Reserve Quantities [Line Items]        
Unevaluated properties $ 1,168,016 $ 668,721 $ 132,181 $ 142,525
Monarch Operating Area [Member]        
Reserve Quantities [Line Items]        
Unevaluated properties 121,096      
WildHorse Operating Area [Member]        
Reserve Quantities [Line Items]        
Unevaluated properties 447,925      
Ranger Operating Area [Member]        
Reserve Quantities [Line Items]        
Unevaluated properties 26,648      
Spur operating areas [Member]        
Reserve Quantities [Line Items]        
Unevaluated properties $ 572,347      
Minimum        
Reserve Quantities [Line Items]        
Unevaluated property costs expected evaluation period range 10 years      
Maximum        
Reserve Quantities [Line Items]        
Unevaluated property costs expected evaluation period range 15 years