Commitments and Contingencies - Additional Information (Detail) $ in Millions		1 Months Ended	12 Months Ended
	Oct. 24, 2017 USD ($)	Oct. 30, 2011 Patents	Dec. 31, 2017 USD ($)	Sep. 28, 2018 USD ($)	Sep. 29, 2017 USD ($)
Other Commitments [Line Items]
Non-cancelable purchase commitments				$ 45.1
Maximum amount of potential future payments under the company's financial guarantees				3.3
Contract Manufacturing [Member]
Other Commitments [Line Items]
Bank Guarantees and Standby Letters of Credit				0.8
Indemnification [Member]
Other Commitments [Line Items]
Accrual for indemnification provisions				0.0
TVN [Member] | Guarantee Obligations [Member]
Other Commitments [Line Items]
Bank Guarantees and Standby Letters of Credit				1.3
Avid [Member]
Other Commitments [Line Items]
Loss Contingency, Patents Allegedly Infringed, Number | Patents		2
Estimated Litigation Liability					$ 6.0
Payments for litigation settlement	$ 2.5
Avid [Member] | Selling, General and Administrative Expenses [Member]
Other Commitments [Line Items]
Litigation Settlement, Expense			$ 6.0
Settled Litigation Payment Second Quarter of 2019 [Member] | Avid [Member]
Other Commitments [Line Items]
Estimated Litigation Liability, Noncurrent				1.5
Settled Litigation Payment Third Quarter of 2020 [Member] | Avid [Member]
Other Commitments [Line Items]
Estimated Litigation Liability, Noncurrent				2.0
Foreign Line of Credit [Member] | Performance Guarantee [Member] | Guarantee Obligations [Member]
Other Commitments [Line Items]
Line of Credit Facility, Current Borrowing Capacity			2.0
Domestic Line of Credit [Member] | Performance Guarantee [Member] | Guarantee Obligations [Member]
Other Commitments [Line Items]
Bank Guarantees and Standby Letters of Credit			$ 2.2
Line of Credit Facility, Fair Value of Amount Outstanding				$ 0.0