CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
CONDENSED CONSOLIDATED BALANCE SHEETS
Natuarl gas and oil properties, using the full cost method, costs excluded from amortization	$ 942.9	$ 712.1
Common Stock, Issued, Shares	349,058,501	347,733,839
Common Stock, Authorized, Shares	1,250,000,000	1,250,000,000
Common Stock, Par Value	$ 0.01	$ 0.01
Common Stock in Treasury, Shares	98,889	156,636