Restructuring and Related Charges - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended	12 Months Ended
		Aug. 31, 2018	Mar. 29, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 346
Payments for Restructuring			1,229
Restructuring Reserve			4,420	$ 5,335
Adjustments to restructuring liability			(12)
Restructuring Reserve, Current			3,200	3,300
Restructuring Reserve, Noncurrent			1,200	2,000
Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring			506
Restructuring Reserve			2,457	2,926
Adjustments to restructuring liability			(37)
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			4,200
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			346
Payments for Restructuring			144
Restructuring Reserve			202	0
Employee Severance [Member] | Harmonic 2019 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			300
Payments for Restructuring			100
Restructuring Reserve			200
TVN Voluntary Departure Plan [Member]
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring	[1]		579
Restructuring Reserve	[1]		1,761	2,409
Adjustments to restructuring liability	[1]		25
TVN [Member]
Restructuring Cost and Reserve [Line Items]
Postemployment Benefits Liability			1,800	$ 2,400
San Jose CA Excess Facility [Member] | Facility Closing [Member] | Harmonic 2018 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 900
Restructuring Reserve			$ 900

[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.