Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Condensed Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts	$ 29,034	$ 29,740
Accumulated depreciation and depletion on Property, plant and equipment	2,537,156	2,454,339
Accumulated amortization of Intangible and other long-term assets	$ 73,228	$ 69,588
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	152,831,563	151,861,661
Common stock, shares outstanding	152,831,563	151,861,661