Supplemental Information On Oil And Gas Exploration And Production Activities (Unaudited) - Changes in Quantities of Proved Oil and natural Gas and NGL Reserves Attributable to Noncontrolling Interests (Details)	Dec. 31, 2018 MBoe MBbls MMBbls MMcf	Dec. 31, 2017 MBoe MBbls MMBbls MMcf
Reserve Quantities [Line Items]
Proved developed | MBoe	13,068	11,318
Proved undeveloped | MBoe	41,560	34,028
Total proved | MBoe	54,628	45,346
Oil (MBbl)
Reserve Quantities [Line Items]
Proved developed reserves, net attributable to noncontrolling interest, volume | MBbls	7,917	6,775
Proved undeveloped reserves, net attributable to noncontrolling interest, volume | MBbls	24,709	20,059
Proved developed and undeveloped reserves, net attributable to noncontrolling interest, volume | MBbls	32,626	26,834
Natural Gas (MMcf)
Reserve Quantities [Line Items]
Proved developed reserves, net attributable to noncontrolling interest, gas | MMcf	14,430	13,232
Proved undeveloped reserves, net attributable to noncontrolling interest, gas | MMcf	48,140	38,415
Proved developed and undeveloped reserves, net attributable to noncontrolling interest, gas | MMcf	62,570	51,647
NGLs (MBbl)
Reserve Quantities [Line Items]
Proved developed reserves, net attributable to noncontrolling interest, volume | MMBbls	2,746	2,338
Proved undeveloped reserves, net attributable to noncontrolling interest, volume | MMBbls	8,828	7,566
Proved developed and undeveloped reserves, net attributable to noncontrolling interest, volume | MMBbls	11,574	9,904