Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2
Revenues from contracts with customers	$ 1,200	$ 1,537
Net loss on commodity derivatives	(91)	(102)
Income from equity method investments	11	37
Net gain on disposal of assets	42	257
Other income	35	4
Less costs and expenses:
Production	187	217
Shipping, handling and other operating	154	130
Exploration	59	52
Depreciation, depletion and amortization	554	590
Impairments	6	8
Taxes other than income	72	64
General and administrative	94	100
Net interest and other	49	45
Other net periodic benefit costs	(5)	3
Income tax provision (benefit)	(147)	168
Net Income (Loss) Attributable to Parent	174	356
Capital expenditures	614	622
Pension Plan
Less costs and expenses:
Other net periodic benefit costs	0	4
Not Allocated to Segments
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0	0
Net loss on commodity derivatives	(113)	(43)
Income from equity method investments	0	0
Net gain on disposal of assets	42	257
Other income	31	0
Less costs and expenses:
Production	(2)	(1)
Shipping, handling and other operating	1	0
Exploration	0	0
Depreciation, depletion and amortization	6	8
Impairments	6	8
Taxes other than income	(2)	0
General and administrative	58	55
Net interest and other	49	45
Other net periodic benefit costs	(3)	5
Income tax provision (benefit)	(134)	(5)
Net Income (Loss) Attributable to Parent	(19)	99
Capital expenditures	3	5
United States E&P
Segment Reporting Information [Line Items]
Revenues from contracts with customers	1,062	1,125
United States E&P | Operating Segments
Segment Reporting Information [Line Items]
Revenues from contracts with customers	1,062	1,125
Net loss on commodity derivatives	22	(59)
Income from equity method investments	0	0
Net gain on disposal of assets	0	0
Other income	1	3
Less costs and expenses:
Production	139	151
Shipping, handling and other operating	140	111
Exploration	59	51
Depreciation, depletion and amortization	514	528
Impairments	0	0
Taxes other than income	74	64
General and administrative	29	36
Net interest and other	0	0
Other net periodic benefit costs	0	0
Income tax provision (benefit)	(2)	3
Net Income (Loss) Attributable to Parent	132	125
Capital expenditures	606	611
Int'l E&P
Segment Reporting Information [Line Items]
Revenues from contracts with customers	138	412
Int'l E&P | Operating Segments
Segment Reporting Information [Line Items]
Revenues from contracts with customers	138	412
Net loss on commodity derivatives	0	0
Income from equity method investments	11	37
Net gain on disposal of assets	0	0
Other income	3	1
Less costs and expenses:
Production	50	67
Shipping, handling and other operating	13	19
Exploration	0	1
Depreciation, depletion and amortization	34	54
Impairments	0	0
Taxes other than income	0	0
General and administrative	7	9
Net interest and other	0	0
Other net periodic benefit costs	(2)	(2)
Income tax provision (benefit)	(11)	170
Net Income (Loss) Attributable to Parent	61	132
Capital expenditures	5	6
Reclassification out of Accumulated Other Comprehensive Income [Member]
Less costs and expenses:
Income tax provision (benefit)	0	0
Net Income (Loss) Attributable to Parent	4	(3)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plan Adjustment, Net Gain (Loss) Due To Settlement, Attributable To Parent [Member]
Less costs and expenses:
Other net periodic benefit costs	$ 0	$ 4