CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Apr. 02, 2017	Apr. 03, 2016	Apr. 02, 2017	Apr. 03, 2016
Income Statement [Abstract]
Net sales	$ 442.9	$ 444.3	$ 878.4	$ 773.5
Cost of sales	158.8	243.7	317.8	385.0
Gross profit	284.1	200.6	560.6	388.5
Operating expenses:
Selling, general and administrative	75.8	113.7	166.2	183.0
Research and development costs	86.9	87.8	169.2	142.7
Amortization of intangible assets	46.5	45.3	92.1	70.7
Restructuring and severance charges	5.8	51.7	8.2	53.4
Total operating expenses	215.0	298.5	435.7	449.8
Operating income	69.1	(97.9)	124.9	(61.3)
Other expense
Interest expense, net	(25.9)	(38.0)	(51.8)	(46.2)
Other expense, net	(0.3)	(77.8)	(1.6)	(78.4)
Total other expense	(26.2)	(115.8)	(53.4)	(124.6)
Income (loss) before income taxes	42.9	(213.7)	71.5	(185.9)
Provision for (benefit from) income taxes	1.7	(1.7)	10.9	2.4
Net income (loss)	$ 41.2	$ (212.0)	$ 60.6	$ (188.3)
Earnings (loss) per share:
Basic (USD per share)	$ 0.36	$ (1.93)	$ 0.53	$ (1.85)
Diluted (USD per share)	$ 0.35	$ (1.93)	$ 0.52	$ (1.85)
Weighted-average common shares outstanding:
Basic (in shares)	114.7	109.6	114.4	102.0
Diluted (in shares)	117.0	109.6	116.6	102.0
Net income (loss)	$ 41.2	$ (212.0)	$ 60.6	$ (188.3)
Other comprehensive income (loss), net of tax:
Translation adjustment	0.3	1.9	(0.9)	2.6
Unrealized actuarial loss on pension benefits	0.0	(0.1)	0.0	(0.1)
Other comprehensive income (loss), net of tax	0.3	1.8	(0.9)	2.5
Total comprehensive income (loss)	$ 41.5	$ (210.2)	$ 59.7	$ (185.8)