Fair Value Measurements - Commodity Derivatives at Fair Value (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Quoted Prices in Active Markets (Level 1)
Net valuation of the Company's derivatives subject to fair value measurement on a recurring basis
Commodity derivatives	$ 0
Significant Other Observable Inputs (Level 2)
Net valuation of the Company's derivatives subject to fair value measurement on a recurring basis
Commodity derivatives	443
Significant Unobservable Inputs (Level 3)
Net valuation of the Company's derivatives subject to fair value measurement on a recurring basis
Commodity derivatives	$ 0