Restructuring Costs Expensed (Details) - Realignment of Office Furniture Facilities and Exit of Business Line - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 2,335	$ 1,130	$ 12,036	$ 4,211
Cost of sales - accelerated depreciation
Restructuring Cost and Reserve [Line Items]
Restructuring costs	1,552	731	8,711	2,154
Restructuring charges
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 783	$ 399	$ 3,325	$ 2,057