Restructuring (Schedule of Restructuring Activities) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	$ 2,447	$ 1,874
Restructuring charges	5,405	1,642
Costs paid or otherwise settled	(3,074)	(994)
Balance at the end of the period	4,778	2,522
Severance & related
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	1,192	801
Restructuring charges	3,964	1,276
Costs paid or otherwise settled	(1,443)	(52)
Balance at the end of the period	3,713	2,025
Lease Termination & Fixed Assets
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	870	1,036
Restructuring charges	440	57
Costs paid or otherwise settled	(593)	(616)
Balance at the end of the period	717	477
Software Contracts & Engineering Tools
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	360	25
Restructuring charges	913	0
Costs paid or otherwise settled	(968)	(25)
Balance at the end of the period	305	0
Other
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	25	12
Restructuring charges	88	309
Costs paid or otherwise settled	(70)	(301)
Balance at the end of the period	$ 43	$ 20