Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Consolidated Balance Sheets
Property, plant and equipment, accumulated depreciation (in dollars)	$ 2,055,204	$ 2,037,598
Preferred stock, authorized shares	10,000,000	10,000,000
Preferred stock, issued shares	0	0
Common stock, authorized shares	200,000,000	200,000,000
Common stock, issued shares	95,853,329	94,690,932
Common stock, outstanding shares	95,853,329	94,690,932