Summary of Significant Accounting Policies - Summary of Unaudited Pro Forma Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	2 Months Ended	3 Months Ended						7 Months Ended	9 Months Ended
	Aug. 13, 2018	Sep. 30, 2018	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Aug. 13, 2018	Sep. 30, 2019	Sep. 30, 2018
Total oil and gas sales	$ 32,588	$ 70,123	$ 224,444						$ 166,630	$ 479,441
Net income (loss)	$ (16,865)	$ 13,823	$ 6,791	$ 21,407	$ 13,575		$ (34,003)	$ (41,886)	$ (92,754)	$ 41,773
Net income per share:
Basic		$ 0.13	$ (0.01)							$ 0.26
Diluted		$ 0.13	$ (0.01)							$ 0.26
Pro Forma
Total oil and gas sales			$ 247,192			$ 293,266				$ 858,042	$ 790,653
Net income (loss)			$ 36,755			$ 54,242				$ 201,338	$ 92,037
Net income per share:
Basic			$ 0.15			$ 0.24				$ 0.93	$ 0.34
Diluted			$ 0.13			$ 0.19				$ 0.72	$ 0.33