Organization and Basis of Presentation - Additional Information (Detail) - Segment	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Consolidation And Basis Of Presentation [Line Items]
Number of reportable business segments	1
Crude Oil Reserves [Member]
Consolidation And Basis Of Presentation [Line Items]
Proved reserves		50.00%
Natural Gas Reserves [Member]
Consolidation And Basis Of Presentation [Line Items]
Proved reserves		35.00%
Natural Gas Liquids Reserves [Member]
Consolidation And Basis Of Presentation [Line Items]
Proved reserves		15.00%