Restructuring and Related Charges - 2016 Activities in Restructuring Accrual (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Production Related Impairments or Charges		$ 115	$ 278	$ 877	$ 786
Restructuring Reserve [Roll Forward]
Beginning Balance				8,000
Restructuring and related charges		631	$ 777	1,717	$ 2,056
Ending Balance		6,100		8,000		$ 8,000
Restructuring Reserve, Current		(3,500)				(4,400)
Restructuring Reserve, Noncurrent		2,600				3,600
Harmonic 2016 Restructuring Plan [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance				7,554
Restructuring and related charges				543
Cash payments				(2,155)
Foreign exchange gain (loss)				(107)
Ending Balance		5,835		7,554		7,554
Restructuring Reserve, Current	[1]	(3,346)
Restructuring Reserve, Noncurrent	[1]	2,489
Harmonic 2016 Restructuring Plan [Member] | Facility Closing [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance				2,426
Restructuring and related charges				66
Cash payments				(502)
Ending Balance		1,990		2,426		2,426
Restructuring Reserve, Current	[1]	(900)
Restructuring Reserve, Noncurrent	[1]	1,090
Harmonic 2016 Restructuring Plan [Member] | TVN Voluntary Departure Plan [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance				5,128
Restructuring and related charges				477
Cash payments				(1,653)
Foreign exchange gain (loss)				(107)
Ending Balance		3,845		$ 5,128		$ 5,128
Restructuring Reserve, Current	[1]	(2,446)
Restructuring Reserve, Noncurrent	[1]	$ 1,399

[1] The current portion and long-term portion of the restructuring liability are reported as components of “Accrued and other current liabilities” and “Other non-current liabilities”, respectively, on the Company’s Condensed Consolidated Balance Sheets.