Restructuring and Related Charges - 2016 Activities in Restructuring Accrual (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 29, 2017	Sep. 30, 2016	Sep. 29, 2017	Sep. 30, 2016
Restructuring Reserve [Roll Forward]
Restructuring and related charges		$ 2,028	$ (27)	$ 4,084	$ 4,488
Harmonic 2016 Restructuring Plan [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance				13,544
Restructuring charges				2,991
Restructuring and related charges				(7)
Cash payments				(9,665)
Foreign exchange gain (loss)				841
Ending Balance		7,704		13,544
Restructuring Reserve, Current	[1]	(4,422)
Restructuring Reserve, Noncurrent	[1]	3,282
Harmonic 2016 Restructuring Plan [Member] | Facility Closing [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance				2,375
Restructuring charges				73
Restructuring and related charges				0
Cash payments				(921)
Ending Balance		1,527		2,375
Restructuring Reserve, Current	[1]	(730)
Restructuring Reserve, Noncurrent	[1]	797
Harmonic 2016 Restructuring Plan [Member] | TVN Voluntary Departure Plan [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	[2]			9,650
Restructuring charges	[2]			1,781
Restructuring and related charges	[2]			0
Cash payments	[2]			(6,232)
Foreign exchange gain (loss)	[2]			805
Ending Balance	[2]	6,004		9,650
Restructuring Reserve, Current	[1],[2]	(3,519)
Restructuring Reserve, Noncurrent	[1],[2]	2,485
Harmonic 2016 Restructuring Plan [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	[3]			1,519
Restructuring charges	[3]			1,137
Restructuring and related charges	[3]			(7)
Cash payments	[3]			(2,512)
Foreign exchange gain (loss)	[3]			36
Ending Balance	[3]	173		$ 1,519
Restructuring Reserve, Current	[3]	(173)
Restructuring Reserve, Noncurrent	[1],[3]	$ 0

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

[2] See discussion of the TVN VDP above for future estimated payments through 2020.

[3] The Company anticipates that the remaining severance and benefits accrual at September 29, 2017 will be fully paid in 2017.