Stockholders' Equity, Stock-Based Compensation Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Natural gas and oil properties	$ 12	$ 18	$ 45	$ 55
General and administrative expenses	13	17	48	55
Natural gas, oil and NGL production expenses	5	6	17	18
Marketing, gathering and compression expenses	2	4	5	12
Oilfield services expenses	3	2	8	8
Total	$ 35	$ 47	$ 123	$ 148