Summary of Significant Accounting Policies - Net Capitalized Costs and Associated Accumulated Depreciation, Depletion & Amortization and Non Cash Impairments (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Proved properties	$ 721,174	$ 725,964
Wells and related equipment and facilities	1,910,527	1,805,136
Support equipment and facilities	105,397	99,540
Materials and supplies	11,944	13,489
Total proved oil and gas properties	2,749,042	2,644,129
Unproved properties	182,605	265,387
Wells and facilities in progress	60,704	92,406
Total unproved oil and gas properties, excluded from amortization	243,309	357,793
Accumulated depreciation, depletion, amortization and impairment	(2,224,428)	(958,475)
Total oil and gas properties, net	$ 767,923	$ 2,043,447