Revenue Impact of ASC 606 in Current Period Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 360,460	$ 331,514	$ 732,493	$ 579,253
Increase (Decrease) in Revenue	(8,172)		(10,184)
COST OF GOODS SOLD	208,660	243,452	431,692	402,246
Increase (Decrease) Cost of Goods Sold	1,020		1,041
Gross Profit	151,800	$ 88,062	300,801	$ 177,007
Increase (Decrease) Gross Profit	7,152		9,143
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	352,288		722,309
COST OF GOODS SOLD	207,640		430,651
Gross Profit	$ 144,648		$ 291,658