Restructuring and Related Charges - 2016 Activities in Restructuring Accrual (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 30, 2018	Mar. 31, 2017	Mar. 30, 2018	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Beginning Balance		$ 8,000
Restructuring and related charges		1,086	$ 1,279
Ending Balance		8,000		$ 7,200	$ 8,000
Restructuring Reserve, Current				(4,300)	(4,400)
Restructuring Reserve, Noncurrent				2,900	3,600
Harmonic 2016 Restructuring Plan [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		7,554
Restructuring and related charges		(7)
Cash payments		(1,131)
Foreign exchange gain (loss)		107
Ending Balance		7,554		6,523	7,554
Restructuring Reserve, Current	[1]			(3,756)
Restructuring Reserve, Noncurrent	[1]			2,767
Harmonic 2016 Restructuring Plan [Member] | Facility Closing [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		2,426
Restructuring and related charges		34
Cash payments		(251)
Ending Balance		2,426		2,209	2,426
Restructuring Reserve, Current	[1]			(892)
Restructuring Reserve, Noncurrent	[1]			1,317
Harmonic 2016 Restructuring Plan [Member] | TVN Voluntary Departure Plan [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		5,128
Restructuring and related charges		(41)
Cash payments		(880)
Foreign exchange gain (loss)		107
Ending Balance		$ 5,128		4,314	$ 5,128
Restructuring Reserve, Current	[1]			(2,864)
Restructuring Reserve, Noncurrent	[1]			$ 1,450

[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.