Change in Accounting Principle - Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013	[2]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment - cost	$ 46,749	$ 46,150	[1]
Less: Accumulated depreciation, depletion, and amortization	(27,882)	(25,312)	[1]
Property and equipment, net	18,867	20,838	[1]
Total assets	22,519	25,500	[1]
Deferred income taxes	1,710	2,529	[1]
Paid-in capital	12,364	12,619	[1]
Accumulated deficit	(3,385)	(1,980)	[1]
Accumulated other comprehensive loss	(112)	(119)	[1]	$ (116)
Noncontrolling interest	1,441	1,602	[1]
TOTAL EQUITY	7,679	9,490	[1],[2]	20,541	[2]	$ 30,756
Change from Full Cost Method to Successful Efforts Method [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment - cost	46,749	46,150
Less: Accumulated depreciation, depletion, and amortization	(27,882)	(25,312)
Property and equipment, net	18,867	20,838
Total assets	22,519	25,500
Deferred income taxes	1,710	2,529
Paid-in capital	12,364	12,619
Accumulated deficit	(3,385)	(1,980)
Accumulated other comprehensive loss	(112)	(119)
Noncontrolling interest	1,441	1,602
TOTAL EQUITY	7,679	9,490
Change from Full Cost Method to Successful Efforts Method [Member] | Under Full Cost [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment - cost	95,371	93,825
Less: Accumulated depreciation, depletion, and amortization	(83,230)	(79,706)
Property and equipment, net	12,141	14,119
Total assets	15,793	18,781
Deferred income taxes	353	1,072
Paid-in capital	12,225	12,467
Accumulated deficit	(8,521)	(7,153)
Accumulated other comprehensive loss	(109)	(116)
Noncontrolling interest	1,344	1,662
TOTAL EQUITY	2,310	4,228
Change from Full Cost Method to Successful Efforts Method [Member] | Changes [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment - cost	(48,622)	(47,675)
Less: Accumulated depreciation, depletion, and amortization	55,348	54,394
Property and equipment, net	6,726	6,719
Total assets	6,726	6,719
Deferred income taxes	1,357	1,457
Paid-in capital	139	152
Accumulated deficit	5,136	5,173
Accumulated other comprehensive loss	(3)	(3)
Noncontrolling interest	97	(60)
TOTAL EQUITY	5,369	5,262
Retained Earnings (Accumulated Deficit) [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
TOTAL EQUITY	$ (3,385)	$ (1,980)	[2]	$ 8,655	[2]	$ 17,395

[1] Financial information for 2015 has been recast to reflect retrospective application of the successful efforts method of accounting. See Note 1.

[2] Financial information for 2015, 2014, and 2013 has been recast to reflect retrospective application of the successful efforts method of accounting. See Note 1.