Natural Gas And Oil Properties (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Discount rate of natural gas and oil reserves	10.00%
Cash flow hedges impact on ceiling value, net of tax	$ 45	$ 40
Henry Hub Natural Gas [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Full cost ceiling test, price	3.88	3.99
Oil [Member] | West Texas Intermediate Oil [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Full cost ceiling test, price	79.21	94.92
NGL [Member] | West Texas Intermediate Oil [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Full cost ceiling test, price	16.38	43.64