Derivative Instruments and Fair Value Measurements - Narrative (Details) - Commodity Contract	3 Months Ended	12 Months Ended
	Mar. 31, 2019 barrel_of_oil_per_day contract	Dec. 31, 2018 barrel_of_oil_per_day contract
Derivative Instruments, Gain (Loss) [Line Items]
Number of contracts held | contract	12	10
April 2019
Derivative Instruments, Gain (Loss) [Line Items]
Production	322
May 2019
Derivative Instruments, Gain (Loss) [Line Items]
Production	258	258
June 2019 through August 2019
Derivative Instruments, Gain (Loss) [Line Items]
Production	322	322
September 2019 through December 2019
Derivative Instruments, Gain (Loss) [Line Items]
Production	516	258
January 2020 through February 2020
Derivative Instruments, Gain (Loss) [Line Items]
Production	258
January through April 2019
Derivative Instruments, Gain (Loss) [Line Items]
Production		322
Reported Value Measurement
Derivative Instruments, Gain (Loss) [Line Items]
Number of contracts held | contract	10