Stockholders' Equity, Stock-Based Compensation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	$ 12	$ 18	$ 32	$ 38
Share Based Compensation General And Administrative Expense	15	20	35	38
Share Based Compensation Natural Gas And Oil Production Expenses	6	5	12	12
Share Based Compensation Allocated To Marketing Gathering And Compression Expense	1	4	4	8
Share Based Compensation Service Operations Expense	2	2	5	5
Allocated Share-based Compensation Expense	$ 36	$ 49	$ 88	$ 101