Revenue Impact of ASC 606 in Current Period Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 327,169	$ 343,236	$ 1,059,662	$ 922,489
Increase (Decrease) in Revenue	13,502		3,318
Cost of goods sold	192,582	231,638	624,274	633,884
Increase (Decrease) Cost of Goods Sold	(3,577)		(2,536)
Gross Profit	134,587	$ 111,598	435,388	$ 288,605
Increase (Decrease) Gross Profit	(9,925)		(782)
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	340,671		1,062,980
Cost of goods sold	196,159		626,810
Gross Profit	$ 144,512		$ 436,170