Impairments - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) Compressor	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($) Rigs
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Leasehold	$ 1,000
Impairment of oil and natural gas properties	5,416	$ 0	$ 15,407	$ 0
Effects of Cash Flow Hedges Considered in Calculation Ceiling Limitation, Amount	184		184
Impairments of fixed assets and other	79	15	167	75
Gain (Loss) on Contract Termination			(7)
Provision for legal contingencies	0	100	359	100
Contractual Dispute [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairments of fixed assets and other	47
Note Receivable [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairments of fixed assets and other	9		22
Net Acreage Shortfall [Member] | Total [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Provision for legal contingencies	70
Other Cost and Expense, Operating		$ 22
Natural Gas Compressors [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairments of fixed assets and other	$ 21
Equipment, Number of Units | Compressor	466
Proceeds from Sale of Property, Plant, and Equipment			$ 63
Drilling Rigs [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairments of fixed assets and other				15
Gain (Loss) on Contract Termination				$ (8)
Leased Equipment Purchased | Rigs				31
Payments to Acquire Property, Plant, and Equipment				$ 140