Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts	$ 32,055	$ 28,242
Accumulated depreciation and depletion on Property, plant and equipment	2,343,681	2,278,856
Accumulated amortization of Intangible and other long-term assets	$ 87,429	$ 83,520
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	151,412,233	150,861,500
Common stock, shares outstanding	151,412,233	150,861,500