Supplemental Oil and Gas Information (Unaudited) - Schedule of Net Reserves (Detail)	12 Months Ended
	Dec. 31, 2020 MBoe MMBoe bbl MMcf	Dec. 31, 2019 MBoe bbl MMcf
Supplemental Oil And Gas Reserve Information [Line Items]
Extensions and discoveries | MMBoe	0.46
Oil [Member]
Supplemental Oil And Gas Reserve Information [Line Items]
Proved developed and undeveloped reserves, Beginning of year	70,772	69,624
Extensions and discoveries	291	301
Production	(3,887)	(3,498)
Revision of previous estimates	(20,500)	(13,084)
Proved developed and undeveloped reserves, End of year	46,676	70,772
Proved developed reserves, Beginning of year	53,476	54,147
Proved developed reserves, End of year	35,613	53,476
Proved undeveloped reserves, Beginning of year	17,296	15,477
Proved undeveloped reserves, End of year	11,063	17,296
Purchase of minerals in place		17,429
Natural Gas [Member]
Supplemental Oil And Gas Reserve Information [Line Items]
Proved developed and undeveloped reserves, Beginning of year | MMcf	377,869	293,959
Extensions and discoveries | MMcf	655	576
Production | MMcf	(27,473)	(26,489)
Revision of previous estimates | MMcf	(76,912)	(92,586)
Proved developed and undeveloped reserves, End of year | MMcf	274,139	377,869
Proved developed reserves, Beginning of year | MMcf	320,731	232,110
Proved developed reserves, End of year | MMcf	252,218	320,731
Proved undeveloped reserves, Beginning of year | MMcf	57,138	61,849
Proved undeveloped reserves, End of year | MMcf	21,921	57,138
Purchase of minerals in place | MMcf		202,409
NGLs [Member]
Supplemental Oil And Gas Reserve Information [Line Items]
Proved developed and undeveloped reserves, Beginning of year	29,252	21,572
Extensions and discoveries	61	44
Production	(1,725)	(1,343)
Revision of previous estimates	(6,104)	(9,554)
Proved developed and undeveloped reserves, End of year	21,484	29,252
Proved developed reserves, Beginning of year	23,646	17,324
Proved developed reserves, End of year	19,009	23,646
Proved undeveloped reserves, Beginning of year	5,606	4,248
Proved undeveloped reserves, End of year	2,475	5,606
Purchase of minerals in place		18,533
Proved Reserves, Total
Supplemental Oil And Gas Reserve Information [Line Items]
Proved developed and undeveloped reserves, Beginning of year | MBoe	163,002	140,189
Production | MBoe	(10,190)	(9,256)
Revision of previous estimates | MBoe	(39,424)	(38,069)
Proved developed and undeveloped reserves, End of year | MBoe	113,849	163,002
Extensions and discoveries | MBoe	461	441
Proved developed reserves, Beginning of year | MBoe	130,577	110,156
Proved developed reserves, End of year | MBoe	96,658	130,577
Proved undeveloped reserves, Beginning of year | MBoe	32,425	30,033
Proved undeveloped reserves, End of year | MBoe	17,191	32,425
Purchase of minerals in place | MBoe		69,697