Supplemental Information on Oil and Gas Producing Activities (Unaudited) - Proved reserves (Details)	12 Months Ended
	Dec. 31, 2021 Bcfe Bcf MMBbls	Dec. 31, 2020 Bcfe MMBbls Bcf	Dec. 31, 2019 Bcfe MMBbls Bcf
Proved developed and undeveloped reserves:
Balance at the beginning of the period | Bcfe	17,635	18,893	18,011
Revisions | Bcfe	1,486	(940)	(1,648)
Extensions, discoveries and other additions | Bcfe	472	1,105	3,705
Production | Bcfe	(1,194)	(1,310)	(1,175)
Sales | Bcfe	(670)	(113)
Balance at the end of the period | Bcfe	17,729	17,635	18,893
Oil and Gas Reserves
Proved developed reserves | Bcfe	12,753	11,873	11,740
Proved undeveloped reserves | Bcfe	4,976	5,762	7,153
VIE, Martica
Proved developed and undeveloped reserves:
Balance at the beginning of the period | Bcfe	254
Balance at the end of the period | Bcfe	167	254
Oil and Gas Reserves
Proved developed reserves | Bcfe	133	181
Proved undeveloped reserves | Bcfe	34	73
Natural gas
Proved developed and undeveloped reserves:
Balance at the beginning of the period | Bcf	10,025	11,494	11,425
Revisions | Bcf	993	(1,280)	(1,735)
Extensions, discoveries and other additions | Bcf	349	799	2,626
Production | Bcf	(826)	(875)	(822)
Sales | Bcf	(337)	(113)
Balance at the end of the period | Bcf	10,204	10,025	11,494
Oil and Gas Reserves
Proved developed reserves | Bcf	7,395	6,901	7,229
Proved undeveloped reserves | Bcf	2,809	3,124	4,265
Natural gas | VIE, Martica
Proved developed and undeveloped reserves:
Balance at the beginning of the period | Bcf	159
Balance at the end of the period | Bcf	101	159
Oil and Gas Reserves
Proved developed reserves | Bcf	78	110
Proved undeveloped reserves | Bcf	23	49
NGLS
Proved developed and undeveloped reserves:
Balance at the beginning of the period	1,236	1,191	1,052
Revisions	77	65	25
Extensions, discoveries and other additions	18	48	169
Production	(58)	(68)	(55)
Sales	(54)
Balance at the end of the period	1,219	1,236	1,191
Oil and Gas Reserves
Proved developed reserves	876	810	731
Proved undeveloped reserves	343	426	460
NGLS | VIE, Martica
Proved developed and undeveloped reserves:
Balance at the beginning of the period	15
Balance at the end of the period	11	15
Oil and Gas Reserves
Proved developed reserves	9	11
Proved undeveloped reserves	2	4
Oil and condensate
Proved developed and undeveloped reserves:
Balance at the beginning of the period	33	42	46
Revisions	6	(8)	(11)
Extensions, discoveries and other additions	2	3	11
Production	(4)	(4)	(4)
Sales	(1)
Balance at the end of the period	36	33	42
Oil and Gas Reserves
Proved developed reserves	17	19	21
Proved undeveloped reserves	19	14	21
Oil and condensate | VIE, Martica
Proved developed and undeveloped reserves:
Balance at the beginning of the period	0.5
Balance at the end of the period	0.4	0.5
Oil and Gas Reserves
Proved developed reserves	0.2	0.3
Proved undeveloped reserves	0.2	0.2