Change in Accounting Principle - Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Property and equipment - cost	$ 46,714	$ 46,150
Less: Accumulated depreciation, depletion, and amortization	(26,571)	(25,312)
Property and equipment, net	20,143	20,838
Deferred charges and other	911	910
Total Assets	24,346	25,500	$ 36,802
Other current liabilities	1,026	1,223
Income taxes	2,308	2,529
Paid-in capital	12,487	12,619
Accumulated deficit	(2,596)	(1,980)
Accumulated other comprehensive loss	(119)	(119)
Noncontrolling interest	1,554	1,602
TOTAL EQUITY	8,696	9,490	$ 18,256	$ 20,541
Under Full Cost [Member]
TOTAL EQUITY		4,228		28,137
Change from Full Cost Method to Successful Efforts Method [Member]
Property and equipment - cost	46,714	46,150
Less: Accumulated depreciation, depletion, and amortization	(26,571)	(25,312)
Property and equipment, net	20,143	20,838
Deferred charges and other	911
Total Assets	24,346	25,500
Income taxes	2,308	2,529
Paid-in capital	12,487	12,619
Accumulated deficit	(2,596)	(1,980)
Accumulated other comprehensive loss	(119)	(119)
Noncontrolling interest	1,554	1,602
TOTAL EQUITY	8,696	9,490
Change from Full Cost Method to Successful Efforts Method [Member] | Under Full Cost [Member]
Property and equipment - cost	94,657	93,825
Less: Accumulated depreciation, depletion, and amortization	(81,920)	(79,706)
Property and equipment, net	12,737	14,119
Deferred charges and other	937
Total Assets	16,966	18,781
Income taxes	796	1,072
Paid-in capital	12,342	12,467
Accumulated deficit	(8,243)	(7,153)
Accumulated other comprehensive loss	(116)	(116)
Noncontrolling interest	1,475	1,662
TOTAL EQUITY	2,828	4,228
Change from Full Cost Method to Successful Efforts Method [Member] | Changes [Member]
Property and equipment - cost	(47,943)	(47,675)
Less: Accumulated depreciation, depletion, and amortization	55,349	54,394
Property and equipment, net	7,406	6,719
Deferred charges and other	(26)
Total Assets	7,380	6,719
Income taxes	1,512	1,457
Paid-in capital	145	152
Accumulated deficit	5,647	5,173		$ (7,600)
Accumulated other comprehensive loss	(3)	(3)
Noncontrolling interest	79	(60)
TOTAL EQUITY	$ 5,868	$ 5,262