Restructuring (Schedule of Restructuring Activities) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	$ 2,447	$ 1,874
Restructuring charges	1,029	66
Costs paid or otherwise settled	(1,724)	(1,360)
Balance at the end of the period	1,752	580
Severance & related
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	1,192	801
Restructuring charges	241	(248)
Costs paid or otherwise settled	(908)	(52)
Balance at the end of the period	525	501
Lease Termination
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	870	1,036
Restructuring charges	13	63
Costs paid or otherwise settled	(85)	(1,049)
Balance at the end of the period	798	50
Software Contracts & Engineering Tools
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	360	25
Restructuring charges	738	0
Costs paid or otherwise settled	(700)	(25)
Balance at the end of the period	398	0
Other
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	25	12
Restructuring charges	37	251
Costs paid or otherwise settled	(31)	(234)
Balance at the end of the period	$ 31	$ 29