Segment Information - Income (Loss) by Segment and Reconciliation to Income Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 31, 2016	Jul. 26, 2015	Jul. 31, 2016	Jul. 26, 2015
Segment Reporting Information [Line Items]
Operating income (loss)	$ 16,427	$ 3,068	$ 29,695	$ 7,952
Items to reconcile segment operating income to consolidated income before taxes
Stock-based compensation expense	6,097	2,335	11,804	8,281
Changes in the fair value of contingent earn-out obligations	(129)	730	(162)	568
Restructuring charge	0	3,564	0	3,564
Environmental reserve			(66)	2,855
Interest expense, net	2,037	1,900	3,967	3,734
Non-operating expense (income), net	136	(117)	181	376
Income before taxes	14,254	1,285	25,547	3,842
Corporate, Non-Segment [Member]
Items to reconcile segment operating income to consolidated income before taxes
Intangible amortization and impairments	6,328	6,177	12,731	12,340
Stock-based compensation expense	6,097	2,335	11,804	8,281
Changes in the fair value of contingent earn-out obligations	(129)	0	(162)	0
Restructuring charge	0	3,564	0	3,564
Environmental reserve	0	520	0	2,855
Other non-segment related expenses	1,551	4,426	2,793	7,585
Amortization of fair value adjustments related to acquired PP&E	308	312	617	903
Interest expense, net	2,037	1,900	3,967	3,734
Non-operating expense (income), net	136	(117)	181	376
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	30,582	20,402	57,478	43,480
Semiconductor Products Group [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	32,497	22,709	59,954	48,038
All others [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	$ (1,915)	$ (2,307)	$ (2,476)	$ (4,558)

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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