Derivative Financial Instruments - Summary of Outstanding Oil and Gas Derivative Contracts and Weighted Average Oil and Gas Prices (Details) - Forecast $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($) $ / MBbls MBbls	Dec. 31, 2018 USD ($) $ / MBbls MBbls	Dec. 31, 2017 USD ($) MMBTU $ / MBbls $ / MMBTU MBbls	Dec. 31, 2016 USD ($) $ / MBbls MBbls
Purchased | Put Option | Natural Gas (MMbtu)
Derivative [Line Items]
Notional (MMbtu) | MMBTU			5,700
Weighted average strike price (in dollars per unit) | $ / MMBTU			2.75
Sold | Put Option | Natural Gas (MMbtu)
Derivative [Line Items]
Notional (MMbtu) | MMBTU			5,700
Weighted average strike price (in dollars per unit) | $ / MMBTU			2.36
Sold | Call Option | Natural Gas (MMbtu)
Derivative [Line Items]
Notional (MMbtu) | MMBTU			5,700
Weighted average strike price (in dollars per unit) | $ / MMBTU			4.02
Crude Oil (MBbls) | Basis Swap Contracts
Derivative [Line Items]
Price differential ($/Bbl) | $ / MBbls	(0.87)	(0.00)	(1.03)	(0.87)
Crude Oil (MBbls) | Midland-Cushing Index | Basis Swap Contracts
Derivative [Line Items]
Notional (MBbl)	758	0	4,290
Crude Oil (MBbls) | Purchased | Put Option
Derivative [Line Items]
Notional (MBbl)	2,160	900	7,248
Weighted average strike price (in dollars per unit) | $ / MBbls	45.03	52.50	49.28
Crude Oil (MBbls) | Sold | Put Option
Derivative [Line Items]
Notional (MBbl)	2,160	900	7,248
Weighted average strike price (in dollars per unit) | $ / MBbls	32.78	40.00	37.62
Crude Oil (MBbls) | Sold | Put Option | Subject to Master Netting Agreement with Counter Party
Derivative [Line Items]
Notional (MBbl)		9,114	9,114	9,114
Fair value of notional MBbls excluded | $	$ 73.8	$ 73.8	$ 73.8	$ 73.8