Acquisitions (Detail) $ / shares in Units, shares in Millions				3 Months Ended								9 Months Ended		12 Months Ended
	May 02, 2016 USD ($)	Apr. 28, 2016 USD ($)	Jan. 15, 2016 USD ($) project shares	Oct. 02, 2016 USD ($)	Jul. 03, 2016 USD ($)	Apr. 03, 2016 USD ($)	Jan. 03, 2016 USD ($)	Sep. 27, 2015 USD ($)	Jun. 28, 2015 USD ($)	Mar. 29, 2015 USD ($)	Dec. 28, 2014 USD ($)	Oct. 02, 2016 USD ($)	Jun. 29, 2014 USD ($) $ / shares	Oct. 02, 2016 USD ($) $ / shares	Sep. 27, 2015 USD ($)	Sep. 28, 2014 USD ($)
Business Acquisition [Line Items]
Goodwill				$ 2,479,400,000				$ 1,139,300,000				$ 2,479,400,000		$ 2,479,400,000	$ 1,139,300,000	$ 885,600,000
Net sales				450,100,000	$ 431,400,000	$ 444,300,000	$ 329,200,000	328,800,000	$ 317,100,000	$ 296,200,000	$ 303,500,000			1,655,000,000	1,245,600,000	1,138,300,000
Business Acquisition, Pro Forma Information [Abstract]
Proceeds from the divestiture or sale of assets														321,000,000	0	$ 0
Gain on divestiture	$ 125,500,000
Disposal Group, Including Discontinued Operation, Assets, Current				13,900,000				$ 0				13,900,000		13,900,000	$ 0
Disposal Group, Including Discontinued Operation, Consideration				31,400,000								31,400,000		31,400,000
Disposal Group, Including Discontinued Operation, Goodwill				$ 7,200,000								7,200,000		7,200,000
PMC-SIERRA INC. [Member]
Business Acquisition [Line Items]
Cost of Goods Sold														66,200,000
Payments to Acquire Businesses, Gross			$ 1,994,383,000
Cash consideration			2,484,900,000
Cash and cash equivalents			313,000,000
Accounts receivable			53,300,000
Inventories			98,200,000
Other current assets			15,800,000
Property and equipment			38,000,000
Other assets			19,700,000
Identifiable intangible assets			747,600,000
Goodwill			1,472,300,000
Current liabilities			(121,600,000)
Long term debt			(87,300,000)
Other non-current liabilities			(64,100,000)
Gross contractual amount of acquired receivables			53,300,000
Asset Amount			747,600,000
Initial purchase price accounting adjustment intangible assets												2,000,000
Initial purchase price accounting adjustment intangible assets current liabilities												17,600,000
Initial purchase price accounting adjustment intangible assets, noncurrent liabilities												3,600,000
Initial purchase price accounting adjustment, deferred income taxes												48,000,000
Initial purchase price accounting adjustment intangible assets, consideration transferred												9,500,000
Initial purchase price accounting adjustment goodwill												$ 41,500,000
Business Acquisition, Pro Forma Information [Abstract]
Net sales														1,804,500,000
Net income (loss)														$ 82,300,000
Basic (usd per share) | $ / shares														$ 0.74
Diluted (usd per share) | $ / shares														$ 0.72
Equity Issued in Business Combination, Fair Value Disclosure			15,700,000
Business Combination, Accrued Cash Consideration			300,000
Business Combination, Restructuring														$ 48,600,000
Business Combination, Acquisition Related Costs														$ 41,100,000
Vitesse
Business Acquisition, Pro Forma Information [Abstract]
Net sales													$ 1,773,900,000
Net income (loss)													$ (168,000,000)
Basic (usd per share) | $ / shares													$ (1.52)
Diluted (usd per share) | $ / shares													$ (1.52)
Completed technology | PMC-SIERRA INC. [Member]
Business Acquisition [Line Items]
Identifiable intangible assets			447,000,000
Asset Amount			$ 447,000,000
Useful life of intangible asset			6 years
Customer relationships | PMC-SIERRA INC. [Member]
Business Acquisition [Line Items]
Identifiable intangible assets			$ 52,000,000
Asset Amount			$ 52,000,000
Useful life of intangible asset			9 years
Other | PMC-SIERRA INC. [Member]
Business Acquisition [Line Items]
Identifiable intangible assets			$ 7,600,000
Asset Amount			$ 7,600,000
Useful life of intangible asset			1 year
Common Stock | PMC-SIERRA INC. [Member]
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares			16.0
Business Acquisition, Pro Forma Information [Abstract]
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned			$ 474,500,000
In Process Research and Development [Member] | PMC-SIERRA INC. [Member]
Business Acquisition [Line Items]
Fair Value Measurements, Valuation Techniques, Number Of Projects | project			4
Identifiable intangible assets			$ 241,000,000
Asset Amount			$ 241,000,000
Maximum | PMC-SIERRA INC. [Member]
Business Acquisition, Pro Forma Information [Abstract]
Business Acquisition, Net Sales Related to Products From Acquisition														25.00%
Maximum | Completed technology
Business Acquisition [Line Items]
Useful life of intangible asset														15 years
Maximum | Completed technology | PMC-SIERRA INC. [Member]
Business Acquisition [Line Items]
Useful life of intangible asset			8 years
Maximum | Customer relationships
Business Acquisition [Line Items]
Useful life of intangible asset														15 years
Maximum | In Process Research and Development [Member] | PMC-SIERRA INC. [Member]
Business Acquisition [Line Items]
Research And Development In Process, Expected Completion			2 years
Minimum | PMC-SIERRA INC. [Member]
Business Acquisition, Pro Forma Information [Abstract]
Business Acquisition, Net Sales Related to Products From Acquisition														20.00%
Minimum | Completed technology
Business Acquisition [Line Items]
Useful life of intangible asset														2 years
Minimum | Completed technology | PMC-SIERRA INC. [Member]
Business Acquisition [Line Items]
Useful life of intangible asset			5 years
Minimum | Customer relationships
Business Acquisition [Line Items]
Useful life of intangible asset														4 years
Minimum | In Process Research and Development [Member] | PMC-SIERRA INC. [Member]
Business Acquisition [Line Items]
Research And Development In Process, Expected Completion			6 months
Microsemi LLC - RF Integrated Solutions (RF LLC) [Member]
Business Acquisition, Pro Forma Information [Abstract]
Proceeds from the divestiture or sale of assets	$ 300,000,000
Remote Radio Head [Member]
Business Acquisition [Line Items]
Proceeds from Divestiture of Businesses, Net of Cash Divested		$ 21,000,000