CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2017	Jan. 01, 2017
Income Statement [Abstract]
Net sales	$ 468.7	$ 435.5
Cost of sales (excluding amortization of intangible assets below)	180.0	159.0
Gross profit	288.7	276.5
Operating expenses
Selling, general and administrative	84.4	90.5
Research and development costs	89.0	82.3
Amortization of intangible assets	50.3	45.5
Restructuring, severance and facilities charges	5.5	2.4
Total operating expenses	229.2	220.7
Operating income	59.5	55.8
Other expense
Interest expense, net	(21.7)	(25.9)
Other expense, net	(3.5)	(1.3)
Total other expense	(25.2)	(27.2)
Income before income taxes	34.3	28.6
Provision for (benefit from) income taxes	(13.6)	9.1
Net income	$ 47.9	$ 19.5
Earnings per share
Basic (USD per share)	$ 0.41	$ 0.17
Diluted (USD per share)	$ 0.40	$ 0.17
Weighted-average common shares outstanding:
Basic (in shares)	116.9	114.0
Diluted (in shares)	118.9	116.3
Net income	$ 47.9	$ 19.5
Other comprehensive income (loss), net of taxes
Translation adjustment	0.4	(1.2)
Other comprehensive income (loss), net of taxes	0.4	(1.2)
Total comprehensive income	$ 48.3	$ 18.3