Acquisitions, Divestitures, and Assets Held for Sale - Divestitures and Assets Held for Sale (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestitures	$ 1,415	$ 4,968	$ 567
Gains (losses) on divestitures, net	(1,022)	1,891	(470)
Soda Ash Joint Venture and Certain U.S. Oil and Gas Properties [Member] | Assets Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gains (losses) on divestitures, net			234
Oil and Gas Exploration and Production Reporting Segment and Midstream Reporting Segment [Member] | Certain Coalbed Methane Assets in the Rockies [Member] | Assets Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestitures	154
Gains (losses) on divestitures, net	(538)
Oil and Gas Exploration and Production Reporting Segment and Midstream Reporting Segment [Member] | Certain U.S. Onshore East Texas Assets [Member] | Assets Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestitures	425
Gains (losses) on divestitures, net	(110)
Original sales price	440
Oil and Gas Exploration and Production Reporting Segment [Member] | Certain EOR Assets in the Rockies [Member] | Assets Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestitures	675
Gains (losses) on divestitures, net	(350)
Original sales price	$ 703
Oil and Gas Exploration and Production Reporting Segment [Member] | Certain EOR Assets in the Rockies [Member] | Assets Held for Sale [Member] | Fair Value, Inputs, Level 2 [Member] | Market Approach Valuation Technique [Member] | Nonrecurring [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Losses on assets held for sale		456
Oil and Gas Exploration and Production Reporting Segment [Member] | Offshore Area 1 in Mozambique [Member] | Assets Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestitures		2,640
Gains (losses) on divestitures, net		$ 1,500
Working interest sold		10.00%
Oil and Gas Exploration and Production Reporting Segment [Member] | Chinese subsidiary [Member] | Assets Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestitures		$ 1,075
Gains (losses) on divestitures, net		510
Oil and Gas Exploration and Production Reporting Segment [Member] | Vito Deepwater Development and Surrounding Exploration Blocks [Member] | Assets Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestitures		500
Gains (losses) on divestitures, net		237
Oil and Gas Exploration and Production Reporting Segment [Member] | Pinedale/Jonah Assets [Member] | Assets Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestitures		$ 581
Oil and Gas Exploration and Production Reporting Segment [Member] | Pinedale/Jonah Assets [Member] | Assets Held for Sale [Member] | Fair Value, Inputs, Level 2 [Member] | Market Approach Valuation Technique [Member] | Nonrecurring [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Losses on assets held for sale			$ 704