CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Accounts receivable, allowance for doubtful accounts	$ 7,855	$ 7,892
Property, plant and equipment, accumulated depreciation, depletion and amortization	$ 7,590,711	$ 6,861,494
Cumulative Preferred Stock, par	$ 100	$ 100
Cumulative Preferred Stock, authorized	400,000	400,000
Cumulative Preferred Stock, issued
Common Stock, par	$ 1.00	$ 1.00
Common Stock, authorized	450,000,000	450,000,000
Common Stock, issued	194,380,426	193,909,200
Treasury stock, shares of Common Stock	123,711	185,992