Derivatives and Financial Instruments - Summary of Fair Value and Classification of Derivative Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Derivatives Fair Value [Line Items]
Gross Fair Value, Assets	$ 21,755	$ 3,879
Effect of Counterparty Netting, Assets	(1,105)	(3,879)
Net Carrying Value on Balance Sheet, Assets	20,650	0
Gross Fair Value, Liabilities	1,105	20,598
Effect of Counterparty Netting, Liabilities	(1,105)	(3,879)
Net Carrying Value on Balance Sheet, Liabilities	0	16,719
Commodity derivative assets
Derivatives Fair Value [Line Items]
Gross Fair Value, Assets	14,434	3,879
Effect of Counterparty Netting, Assets	(1,105)	(3,879)
Net Carrying Value on Balance Sheet, Assets	13,329	0
Deferred charges and other long-term assets
Derivatives Fair Value [Line Items]
Gross Fair Value, Assets	7,321	0
Effect of Counterparty Netting, Assets	0	0
Net Carrying Value on Balance Sheet, Assets	7,321	0
Commodity derivative liabilities
Derivatives Fair Value [Line Items]
Gross Fair Value, Liabilities	1,105	20,116
Effect of Counterparty Netting, Liabilities	(1,105)	(3,879)
Net Carrying Value on Balance Sheet, Liabilities	0	16,237
Commodity derivative liabilities
Derivatives Fair Value [Line Items]
Gross Fair Value, Liabilities	0	482
Effect of Counterparty Netting, Liabilities	0	0
Net Carrying Value on Balance Sheet, Liabilities	$ 0	$ 482