Equity - AOCI Reclassifications Table (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Oil, natural gas and NGL reserves, reclassifications from AOCI	$ 993	$ 1,543
Total reclassification from AOCI	(921)	(3,720)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total reclassification from AOCI	4	10
Commodity Contract [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Oil, natural gas and NGL reserves, reclassifications from AOCI	$ 4	$ 10