CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2017		Oct. 01, 2016	Oct. 03, 2015
Income Statement [Abstract]
Net revenue	$ 809,041		$ 627,192	$ 536,471
Cost of sales	426,947		346,156	284,524
Gross profit	382,094		281,036	251,947
Selling, general and administrative	133,601		134,709	123,323
Research and development	100,203		92,374	90,033
Impairment charges	35,207		0	0
Operating expenses	269,011		227,083	213,356
Income from operations	113,083		53,953	38,591
Interest income	6,491		3,318	1,637
Interest expense	(1,059)		(1,107)	(1,183)
Income from operations before income taxes	118,515		56,164	39,045
Income tax (benefit) / expense	(7,394)		7,709	(12,867)
Share of results of equity-method investee, net of tax	(190)		0	0
Net income	$ 126,099		$ 48,455	$ 51,912
Net income per share:
Basic (in dollars per share)	$ 1.78	[1]	$ 0.69	$ 0.69
Diluted (in dollars per share)	$ 1.75	[1]	$ 0.68	$ 0.69
Weighted average shares outstanding:
Basic (in shares)	70,906		70,477	75,414
Diluted (in shares)	72,063		70,841	75,659

[1] EPS for the year may not equal the sum of quarterly EPS due to changes in weighted share calculations.