Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) segment	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Goodwill, Impairment Loss	$ 95	$ 0
Number of reportable segments | segment	2
Revenues from contracts with customers	$ 1,024	1,200
Net gain (loss) on commodity derivatives	202	(91)
Income (loss) from equity method investments	(12)	11
Net gain on disposal of assets	9	42
Other income	7	35
Less costs and expenses:
Production	160	187
Shipping, handling and other operating	144	154
Exploration	28	59
Depreciation, depletion and amortization	644	554
Impairments	97	6
Taxes other than income	66	72
General and administrative	76	94
Net interest and other	64	49
Other net periodic benefit costs	0	(5)
Income tax provision (benefit)	(3)	(147)
Net income (loss)	(46)	174
Assets	19,715	21,410	$ 20,245
Capital expenditures	568	614
Pension Plan
Less costs and expenses:
Other net periodic benefit costs	2
Not Allocated to Segments
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0	0
Net gain (loss) on commodity derivatives	171	(113)
Income (loss) from equity method investments	0	0
Net gain on disposal of assets	9	42
Other income	1	31
Less costs and expenses:
Production	0	(2)
Shipping, handling and other operating	1	1
Exploration	0	0
Depreciation, depletion and amortization	6	6
Impairments	97	6
Taxes other than income	0	(2)
General and administrative	40	58
Net interest and other	64	49
Other net periodic benefit costs	0	(3)
Income tax provision (benefit)	(2)	(134)
Net income (loss)	(25)	(19)
Assets	857	1,239
Capital expenditures	7	3
United States E&P
Segment Reporting Information [Line Items]
Revenues from contracts with customers	970	1,062
United States E&P | Operating Segments
Segment Reporting Information [Line Items]
Revenues from contracts with customers	970	1,062
Net gain (loss) on commodity derivatives	31	22
Income (loss) from equity method investments	0	0
Net gain on disposal of assets	0	0
Other income	4	1
Less costs and expenses:
Production	143	139
Shipping, handling and other operating	140	140
Exploration	28	59
Depreciation, depletion and amortization	617	514
Impairments	0	0
Taxes other than income	66	74
General and administrative	32	29
Net interest and other	0	0
Other net periodic benefit costs	0	0
Income tax provision (benefit)	(1)	(2)
Net income (loss)	(20)	132
Assets	17,453	17,503
Capital expenditures	561	606
Int'l E&P
Segment Reporting Information [Line Items]
Revenues from contracts with customers		138
Int'l E&P | Operating Segments
Segment Reporting Information [Line Items]
Revenues from contracts with customers	54	138
Net gain (loss) on commodity derivatives	0	0
Income (loss) from equity method investments	(12)	11
Net gain on disposal of assets	0	0
Other income	2	3
Less costs and expenses:
Production	17	50
Shipping, handling and other operating	3	13
Exploration	0	0
Depreciation, depletion and amortization	21	34
Impairments	0	0
Taxes other than income	0	0
General and administrative	4	7
Net interest and other	0	0
Other net periodic benefit costs	0	(2)
Income tax provision (benefit)	0	(11)
Net income (loss)	(1)	61
Assets	1,405	2,668
Capital expenditures	0	5
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	$ 2	$ 0