Organization and Nature of Business - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Percentage of crude oil and natural gas production concentrated in crude oil	56.00%
Percentage of crude oil and natural gas revenue concentrated in crude oil	82.00%
North Region [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Percentage of operations concentrated in geographic areas	59.00%
Percentage of revenues concentrated in geographic areas	74.00%
South Region [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Percentage of operations concentrated in geographic areas	41.00%
Percentage of revenues concentrated in geographic areas	26.00%