Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Condensed Consolidated Balance Sheets [Abstract]
Trade accounts receivable, less allowance for doubtful accounts	$ 26,152	$ 16,916
Property, plant and equipment, less allowance for depreciation	$ 792,216	$ 732,390
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	450,000,000	450,000,000
Common stock, shares issued	155,100,768	155,651,116