Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 04, 2015	Jun. 28, 2014	Jul. 04, 2015	Jun. 28, 2014
Restructuring Cost and Reserve [Line Items]
Recorded restructuring charges - less than	$ 4,068	$ 3	$ 8,962	$ 14
Restructuring Reserve [Roll Forward]
Balance at beginning of the period			182	532
Restructuring Charges			8,962	10
Costs Paid or Otherwise Settled			(5,554)	(328)
Adjustments to prior restructuring costs			0	4
Balance at the end of the period	3,590	218	3,590	218
Severance and related
Restructuring Reserve [Roll Forward]
Balance at beginning of the period			0	17
Restructuring Charges			6,909	0
Costs Paid or Otherwise Settled			(4,503)	(8)
Adjustments to prior restructuring costs			0	(9)
Balance at the end of the period	2,406	0	2,406	0
Lease Termination
Restructuring Reserve [Roll Forward]
Balance at beginning of the period			43	368
Restructuring Charges			688	1
Costs Paid or Otherwise Settled			(313)	(304)
Adjustments to prior restructuring costs			0	13
Balance at the end of the period	418	78	418	78
Systems & Engineering Tools
Restructuring Reserve [Roll Forward]
Balance at beginning of the period			0	0
Restructuring Charges			1,303	0
Costs Paid or Otherwise Settled			(537)	0
Adjustments to prior restructuring costs			0	0
Balance at the end of the period	766	0	766	0
Other
Restructuring Reserve [Roll Forward]
Balance at beginning of the period			139	147
Restructuring Charges			62	9
Costs Paid or Otherwise Settled			(201)	(16)
Adjustments to prior restructuring costs			0	0
Balance at the end of the period	0	140	0	140
2012 restructuring plan
Restructuring Cost and Reserve [Line Items]
Recorded restructuring charges - less than	4,100	$ 0	9,000	$ 0
Minimum
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	20,000		20,000
Maximum
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	$ 25,000		$ 25,000