Derivative Instruments and Hedging Activities (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Asset Derivative Instruments	$ 0	$ 592
Liability Derivative Instruments	116	0
Cash (Received) Paid in Settlement of Commodity Derivative Instruments	139	(501)	$ (976)
Total Cash Received in Settlement of Commodity Derivative Instruments	(569)	(1,009)	(29)
Total Non-cash Portion of Loss (Gain) on Commodity Derivative Instruments	708	508	(947)
Total Loss (Gain) on Commodity Derivative Instruments	139	(501)	(976)
Crude Oil
Derivatives, Fair Value [Line Items]
Cash (Received) Paid in Settlement of Commodity Derivative Instruments	(499)	(844)	(34)
Total Non-cash Portion of Loss (Gain) on Commodity Derivative Instruments	582	423	(863)
Total Loss (Gain) on Commodity Derivative Instruments	83	(421)	(897)
Natural Gas
Derivatives, Fair Value [Line Items]
Cash (Received) Paid in Settlement of Commodity Derivative Instruments	(70)	(147)	5
Total Non-cash Portion of Loss (Gain) on Commodity Derivative Instruments	126	65	(84)
Total Loss (Gain) on Commodity Derivative Instruments	56	(82)	(79)
Natural Gas Liquids
Derivatives, Fair Value [Line Items]
Cash (Received) Paid in Settlement of Commodity Derivative Instruments	0	(18)	0
Total Non-cash Portion of Loss (Gain) on Commodity Derivative Instruments	0	20	0
Total Loss (Gain) on Commodity Derivative Instruments	0	2	$ 0
Current Assets
Derivatives, Fair Value [Line Items]
Asset Derivative Instruments	0	582
Current Liabilities
Derivatives, Fair Value [Line Items]
Liability Derivative Instruments	102	0
Noncurrent Assets
Derivatives, Fair Value [Line Items]
Asset Derivative Instruments	0	10
Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Liability Derivative Instruments	$ 14	$ 0