Restructuring and Related Charges - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 28, 2019	Jun. 29, 2018	Jun. 28, 2019	Jun. 29, 2018	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		$ 76	$ 82	$ 153	$ 164
Restructuring charges				701
Payments for Restructuring				2,218
Restructuring Reserve		3,436		3,436		$ 5,335
Adjustments to restructuring liability				(24)
Restructuring Reserve, Current		3,100		3,100		3,300
Restructuring Reserve, Noncurrent		300		300		2,000
Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring				955
Restructuring Reserve		1,636		1,636		2,926
Adjustments to restructuring liability				(47)
Facility Closing [Member] | Harmonic 2017 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Adjustments to restructuring liability						200
Facility Closing [Member] | Prior Restructuring Plans [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve		3,000		3,000
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				433
Payments for Restructuring				284
Restructuring Reserve		149		149		0
Employee Severance [Member] | Harmonic 2019 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		100		400
Payments for Restructuring				300
Restructuring Reserve		100		100
TVN Voluntary Departure Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	[1]			27
Payments for Restructuring	[1]			979
Restructuring Reserve	[1]	1,410		1,410		2,409
Adjustments to restructuring liability	[1]			23
TVN [Member]
Restructuring Cost and Reserve [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)					$ 500
Postemployment Benefits Liability		$ 1,400		$ 1,400		$ 2,400

[1] “TVN VDP” consists of restructuring-related costs in connection with the TVN acquisition that included global workforce reductions, exiting certain operating facilities and disposing of excess assets and an employee voluntary departure plan in France.