Annual report pursuant to Section 13 and 15(d)

Fair Value Measurement (Details)

v3.8.0.1
Fair Value Measurement (Details)
$ in Thousands
1 Months Ended 12 Months Ended
Sep. 30, 2015
USD ($)
bbl
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Reconciliation of changes in Level 3 financial liabilities measured at fair value on a recurring basis      
Beginning balance   $ 194,538 $ 178,049
Accretion and change in fair value   13,476 16,489
Ending balance   208,014 $ 194,538
Level 2 | 5.375% Senior Notes due 2024      
Fair value measurement      
Debt instrument fair value   $ 669,500  
Contribution Agreement | Contingent Consideration Period One      
Fair value measurement      
Contingent consideration $ 125,000    
Threshold number of barrels of water to trigger contingent consideration payment | bbl 176,295,000    
Contribution Agreement | Contingent Consideration Period Two      
Fair value measurement      
Contingent consideration $ 125,000    
Threshold number of barrels of water to trigger contingent consideration payment | bbl 219,200,000