Summary of Quarterly Financial Data (unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

Summary of Quarterly Financial Data (unaudited) [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

The following is a condensed summary of our quarterly results (in thousands, except net income per share amounts). Quarterly diluted net income per share amounts may not total to the respective annual amount due to changes in weighted-average shares outstanding during the year. 

2016	First		Second		Third		Fourth		Fiscal Year
Net sales	$	352,980	$	276,878	$	367,988	$	313,445	$	1,311,291
Gross profit	209,074		171,261		232,343		197,482		810,160
Operating income	19,898		2,396		39,044		15,312		76,650
Net income	12,969		1,416		25,745		11,287		51,417
Net income per share – diluted	$	0.27	$	0.03	$	0.56	$	0.25	$	1.10

2015	First		Second		Third		Fourth			Fiscal Year
Net sales	$	349,809	$	275,289	$	373,919	$	214,682		$	1,213,699
Gross profit	215,833		170,539		233,636		120,743			740,751
Operating income (loss)	43,725		16,629		45,399		(30,657		)	75,096
Net income (loss)	28,799		11,038		31,854		(21,172		)	50,519
Net income (loss) per share – diluted	$	0.54	$	0.21	$	0.62	$	(0.42	)	$	0.97