Consolidated Balance Sheet (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
ASSETS
Property and equipment, at cost, based on the full cost method of accounting for oil and gas properties	$ 1,438	$ 1,300
Stockholders' equity:
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	137,469,404	136,682,631
Treasury stock, shares	256,984	460,914
Commitments and Contingencies (Note 12)	$ 0	$ 0