CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
CONDENSED CONSOLIDATED BALANCE SHEETS
Natural gas and oil properties, using the full cost method, costs excluded from amortization	$ 1,035.6	$ 942.9
Common Stock, Par Value	$ 0.01	$ 0.01
Common Stock, Authorized, Shares	1,250,000,000	1,250,000,000
Common Stock, Issued, Shares	349,214,796	349,058,501
Common Stock in Treasury, Shares	101,659	98,889