Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Trade accounts and notes receivable, allowance for doubtful accounts	$ 1,247	$ 893
Property, plant and equipment, accumulated depreciation	510,316	461,222
Intangible assets, Accumulated amortization	392,262	343,088
Unamortized discount and debt issuance costs	$ 9,920	$ 11,137
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	135,141,486	136,179,381
Common stock, shares outstanding	134,939,086	135,976,981
Treasury stock, shares outstanding	202,400	202,400