Commitments - Narrative (Details) $ in Millions	6 Months Ended
	Jun. 30, 2015 USD ($) Crew	Dec. 31, 2014 USD ($)	Jul. 20, 2011 USD ($)
Long-term Purchase Commitment [Line Items]
Gathering Fee Escalation Rate	15.00%
Investments	$ 255	$ 265
Sundrop Fuels Inc [Member]
Long-term Purchase Commitment [Line Items]
Investments	155		$ 155
Marketable Securities, Equity Securities	25
Drilling Rig Leases [Member]
Long-term Purchase Commitment [Line Items]
Contractual Obligation	$ 353
Drilling Rig Leases [Member] | Minimum [Member]
Long-term Purchase Commitment [Line Items]
Lease Term	3 months
Drilling Rig Leases [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Lease Term	3 years
Pressure Pumping Leases [Member] | Seven Seven Energy Inc. [Member]
Long-term Purchase Commitment [Line Items]
Percent of Total	50.00%
Operating Leases, Future Minimum Payments Due	$ 185
Pressure Pumping Leases [Member] | Pressure Pumping Crew Year One of Agreement [Member] | Seven Seven Energy Inc. [Member]
Long-term Purchase Commitment [Line Items]
Number of Crews | Crew	7
Year of Service Agreement	1 year
Pressure Pumping Leases [Member] | Pressure Pumping Crew Year Two of Agreement [Member] | Seven Seven Energy Inc. [Member]
Long-term Purchase Commitment [Line Items]
Number of Crews | Crew	5
Year of Service Agreement	2 years
Pressure Pumping Leases [Member] | Pressure Pumping Crew Year Three of Agreement [Member] | Seven Seven Energy Inc. [Member]
Long-term Purchase Commitment [Line Items]
Number of Crews | Crew	3
Year of Service Agreement	3 years