Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2015	Sep. 27, 2014	Oct. 03, 2015	Sep. 27, 2014
Restructuring Cost and Reserve [Line Items]
Recorded restructuring charges - less than	$ 6,818	$ 2	$ 15,780	$ 16
Restructuring Reserve [Roll Forward]
Balance at beginning of the period			182	532
Restructuring charges			15,780	10
Costs paid or otherwise settled			(8,257)	(351)
Adjustments to prior restructuring costs			0	6
Balance at the end of the period	7,705	197	7,705	197
Severance and related
Restructuring Reserve [Roll Forward]
Balance at beginning of the period			0	17
Restructuring charges			12,491	0
Costs paid or otherwise settled			(5,825)	(8)
Adjustments to prior restructuring costs			0	(9)
Balance at the end of the period	6,666	0	6,666	0
Lease Termination
Restructuring Reserve [Roll Forward]
Balance at beginning of the period			43	368
Restructuring charges			1,107	1
Costs paid or otherwise settled			(560)	(325)
Adjustments to prior restructuring costs			0	15
Balance at the end of the period	590	59	590	59
Systems & Engineering Tools
Restructuring Reserve [Roll Forward]
Balance at beginning of the period			0	0
Restructuring charges			2,000	0
Costs paid or otherwise settled			(1,551)	0
Adjustments to prior restructuring costs			0	0
Balance at the end of the period	449	0	449	0
Other
Restructuring Reserve [Roll Forward]
Balance at beginning of the period			139	147
Restructuring charges			182	9
Costs paid or otherwise settled			(321)	(18)
Adjustments to prior restructuring costs			0	0
Balance at the end of the period	0	138	0	138
March 2015 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Recorded restructuring charges - less than	1,400		10,300
September 2015 Reduction [Member] | Severance and related
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	6,000		6,000
2012 restructuring plan
Restructuring Cost and Reserve [Line Items]
Recorded restructuring charges - less than	5,500	$ 100		$ 0
Minimum
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	14,000		14,000
Maximum
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost	$ 19,000		$ 19,000