Derivative Instruments and Hedging Activities - Derivative Instruments Summary (Details)	Dec. 31, 2017 bbl / d MMBTU / d $ / MMBTU $ / bbl
Crude Oil Commodity Contract | Three Way Collars - NYMEX WTI 2018
Derivative [Line Items]
Volume Per Day | bbl / d	10,000
Weighted Average Short Put Price	45.50
Weighted Average Floor Price	52.50
Weighted Average Ceiling Price	69.09
Crude Oil Commodity Contract | Swaps - NYMEX WTI 2018
Derivative [Line Items]
Volume Per Day | bbl / d	24,000
Weighted Average Fixed Price	57.09
Crude Oil Commodity Contract | Two Way Collars - NYMEX WTI 2018
Derivative [Line Items]
Volume Per Day | bbl / d	18,000
Weighted Average Floor Price	50.42
Weighted Average Ceiling Price	58.82
Crude Oil Commodity Contract | Three Way Collars - Dated Brent 2018
Derivative [Line Items]
Volume Per Day | bbl / d	3,000
Weighted Average Short Put Price	40.00
Weighted Average Floor Price	50.00
Weighted Average Ceiling Price	70.41
Crude Oil Commodity Contract | Swaps - ICE Brent 2018
Derivative [Line Items]
Volume Per Day | bbl / d	2,000
Weighted Average Fixed Price	59.00
Crude Oil Commodity Contract | Two Way Collars - ICE Brent 2018
Derivative [Line Items]
Volume Per Day | bbl / d	2,000
Weighted Average Floor Price	50.00
Weighted Average Ceiling Price	55.25
Crude Oil Commodity Contract | Three Way Collars - ICE Brent 2018
Derivative [Line Items]
Volume Per Day | bbl / d	5,000
Weighted Average Short Put Price	43.00
Weighted Average Floor Price	50.00
Weighted Average Ceiling Price	59.50
Crude Oil Commodity Contract | Basic Swap 2018
Derivative [Line Items]
Volume Per Day | bbl / d	12,000
Weighted Average Fixed Price	(0.60)
Crude Oil Commodity Contract | Swaps - NYMEX WTI 2019
Derivative [Line Items]
Volume Per Day | bbl / d	3,000
Weighted Average Fixed Price	55.07
Crude Oil Commodity Contract | Swaps - ICE Brent 2019
Derivative [Line Items]
Volume Per Day | bbl / d	5,000
Weighted Average Fixed Price	57.00
Crude Oil Commodity Contract | Three Way Collar - ICE Brent 2019
Derivative [Line Items]
Volume Per Day | bbl / d	3,000
Weighted Average Short Put Price	43.00
Weighted Average Floor Price	50.00
Weighted Average Ceiling Price	64.07
Crude Oil Commodity Contract | Basic Swap 2019
Derivative [Line Items]
Volume Per Day | bbl / d	12,000
Weighted Average Fixed Price	(1.01)
Natural Gas Commodity Contract | Three Way Collars - NYMEX HH 2018
Derivative [Line Items]
Volume Per Day | MMBTU / d	120,000
Weighted Average Short Put Price | $ / MMBTU	2.50
Weighted Average Floor Price | $ / MMBTU	2.88
Weighted Average Ceiling Price | $ / MMBTU	3.65