Quantitative Information about Level 3 Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Fair Value, Option, Quantitative Disclosures [Line Items]
Liability Value	$ (70)
Stockholder Value Appreciation Program [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Liability Value	(46)
SBC Expected Volatility Rate, Maximum	34.50%
Natural gas contracts [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative Liability, Fair Value, Total	(19)
Oil contracts [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative Liability, Fair Value, Total	(201)
Options Held [Member] | Natural gas contracts [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative Liability, Fair Value, Total	(1)
Options Held [Member] | Natural gas contracts [Member] | Maximum [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Credit Risk	0.90%
Fair Value Assumptions Expected Volatility Curves	49.14%
Options Held [Member] | Natural gas contracts [Member] | Minimum [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Credit Risk	0.01%
Fair Value Assumptions Expected Volatility Curves	20.77%
Options Held [Member] | Oil contracts [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative Liability, Fair Value, Total	$ (23)
Options Held [Member] | Oil contracts [Member] | Maximum [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Credit Risk	3.11%
Fair Value Assumptions Expected Volatility Curves	52.25%
Options Held [Member] | Oil contracts [Member] | Minimum [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Credit Risk	0.01%
Fair Value Assumptions Expected Volatility Curves	11.76%