Acquisition Proforma Information (Details) - SPG - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Business Acquisition [Line Items]
Net sales	$ 398,597	$ 364,881	$ 1,202,552	$ 1,058,330
Net income	$ 55,609	$ 38,861	$ 186,224	$ 91,894
Net income per common share - basic	$ 0.39	$ 0.27	$ 1.32	$ 0.65
Net income per common share - diluted	$ 0.39	$ 0.27	$ 1.30	$ 0.64