Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts	$ 22,748	$ 22,076
Accumulated depreciation and depletion on Property, plant and equipment	2,245,051	2,269,542
Accumulated amortization of Intangible and other long-term assets	$ 80,486	$ 81,386
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	150,749,697	149,648,826
Common stock, shares outstanding	150,749,697	149,708,825