Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Trade accounts and notes receivable, allowance for doubtful accounts	$ 2,253	$ 2,474
Property, plant and equipment, accumulated depreciation	419,277	387,523
Intangible assets, Accumulated amortization	274,787	237,207
Unamortized discount and debt issuance costs	$ 7,385	$ 9,173
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	141,473,733	141,319,964
Common stock, shares outstanding	141,473,733	141,319,964