Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 477,565	$ 346,073
Cost of sales	260,542	204,559
Gross profit	217,023	141,514
Operating expenses:
Research and development	31,392	27,084
Selling, general and administrative	73,437	73,768
Gain from business combination	0	(5,416)
Impairment of assets held for sale	265	0
Amortization of intangible assets	2,606	3,878
Total operating expenses	107,700	99,314
Income from operations	109,323	42,200
Other income (expense):
Interest income	471	143
Interest expense	(8,747)	(7,964)
Other—net	(224)	12,993
Total other income (expense), net	(8,500)	5,172
Income from continuing operations before income taxes	100,823	47,372
Provision for income taxes	58,920	16,674
Net income from continuing operations	41,903	30,698
Loss from discontinued operations, net of income taxes	(2)	(290)
Net income	$ 41,901	$ 30,408
Basic net income per share:
Income per share from continuing operations (in USD per share)	$ 1.70	$ 1.26
Loss per share from discontinued operations, net of income taxes (in USD per share)	0.00	(0.01)
Net income per share (in USD per share)	1.70	1.25
Diluted net income per share:
Income per share from continuing operations (in USD per share)	1.67	1.25
Loss per share from discontinued operations, net of income taxes (in USD per share)	0.00	(0.01)
Net income per share (in USD per share)	$ 1.67	$ 1.23
Shares used in computation:
Basic (shares)	24,635	24,347
Diluted (shares)	25,025	24,644