Segment Information - Income (Loss) by Segment and Reconciliation to Income Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Oct. 25, 2015	Jul. 26, 2015	Oct. 26, 2014	Oct. 25, 2015	Oct. 26, 2014
Segment Reporting Information [Line Items]
Operating income	$ 18,898		$ 22,810	$ 26,850	$ 56,016
Items to reconcile segment operating income to consolidated income before taxes
Stock-based compensation expense	5,117		7,935	13,397	21,056
Restructuring charge	962	$ 3,500	0	4,526	1,001
Changes in the fair value of contingent earn-out obligations	(14,186)		(228)	(13,618)	(228)
Environmental reserve				2,855	(58)
Interest expense, net	1,964		1,462	5,698	4,437
Non-operating (income) expense, net	777		(216)	1,152	407
Income before taxes	16,157		21,564	20,000	51,172
Corporate, Non-Segment [Member]
Items to reconcile segment operating income to consolidated income before taxes
Intangible amortization and impairments	6,308		6,423	18,648	19,292
Stock-based compensation expense	5,117		7,935	13,397	21,056
Inventory write-down	0		0	0	1,052
Restructuring charge	962		0	4,526	1,001
Changes in the fair value of contingent earn-out obligations	(14,186)		(228)	(13,618)	(228)
Environmental reserve	0		235	2,855	235
Other non-segment related expenses	2,792		(769)	10,073	(268)
Amortization of fair value adjustments related to acquired PP&E	310		314	948	993
Interest expense, net	1,964		1,462	5,698	4,437
Non-operating (income) expense, net	777		(216)	1,152	407
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating income	20,201		36,720	63,679	99,149
Semiconductor Products Group [Member]
Segment Reporting Information [Line Items]
Operating income	22,019		39,905	70,054	106,383
All others [Member]
Segment Reporting Information [Line Items]
Operating income	$ (1,818)		$ (3,185)	$ (6,375)	$ (7,234)