Harmonic (HLIT) 10-Q 3 Nov 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 26, 2014	Oct. 17, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	26-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'HLIT	'
Entity Registrant Name	'HARMONIC INC	'
Entity Central Index Key	'0000851310	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	88,059,028

CONDENSED_CONSOLIDATED_BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$42,028	$90,329
Short-term investments	55,151	80,252
Accounts receivable, net	75,640	75,052
Inventories	32,512	36,926
Deferred income taxes	2,631	24,650
Prepaid expenses and other current assets	26,852	21,521
Total current assets	234,814	328,730
Property and equipment, net	30,814	34,945
Goodwill	198,007	198,022
Intangibles, net	12,740	31,119
Other assets	13,347	13,268
Total assets	489,722	606,084
Current liabilities:	'	'
Accounts payable	21,377	22,380
Income taxes payable	307	331
Deferred revenue	35,095	27,020
Accrued liabilities	31,043	35,349
Total current liabilities	87,822	85,080
Income taxes payable, long-term	4,199	15,165
Other non-current liabilities	17,554	11,673
Total liabilities	109,575	111,918
Commitments and contingencies (Note 16)	'	'
Stockholders’ equity:	'	'
Preferred stock, $0.001 par value, 5,000 shares authorized; no shares issued or outstanding	0	0
Common stock, $0.001 par value, 150,000 shares authorized; 88,408 and 99,413 shares issued and outstanding at September 26, 2014 and December 31, 2013, respectively	88	99
Additional paid-in capital	2,264,422	2,336,275
Accumulated deficit	-1,883,393	-1,841,999
Accumulated other comprehensive loss	-970	-209
Total stockholders’ equity	380,147	494,166
Total liabilities and stockholders’ equity	$489,722	$606,084

CONDENSED_CONSOLIDATED_BALANCE1

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Sep. 26, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]	'	'
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	88,408,000	99,413,000
Common stock, shares outstanding	88,408,000	99,413,000

CONDENSED_CONSOLIDATED_STATEME

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Income Statement [Abstract]	'	'	'	'
Product revenue	$84,583	$98,713	$259,371	$277,965
Service revenue	23,478	24,205	66,311	63,753
Net revenue	108,061	122,918	325,682	341,718
Product cost of revenue	41,802	52,747	134,336	146,916
Service cost of revenue	12,831	13,379	35,789	33,953
Total cost of revenue	54,633	66,126	170,125	180,869
Gross profit	53,428	56,792	155,557	160,849
Operating expenses:	'	'	'	'
Research and development	22,803	24,560	70,176	75,631
Selling, general and administrative	32,114	32,527	98,640	100,220
Amortization of intangibles	1,661	2,001	5,329	6,099
Restructuring and related charges	388	259	821	925
Total operating expenses	56,966	59,347	174,966	182,875
Loss from operations	-3,538	-2,555	-19,409	-22,026
Interest income, net	47	47	191	141
Other income (expense), net	-261	230	-376	-70
Loss from continuing operations before income taxes	-3,752	-2,278	-19,594	-21,955
Provision for (benefit from) income taxes	-4,830	-38,953	21,800	-45,723
Income (loss) from continuing operations	1,078	36,675	-41,394	23,768
Income from discontinued operations, net of taxes (including gain on disposal of $14,813, net of taxes, for the nine months ended September 27, 2013)	0	91	0	15,619
Net income (loss)	$1,078	$36,766	($41,394)	$39,387
Basic net income (loss) per share from:	'	'	'	'
Continuing operations	$0.01	$0.36	($0.44)	$0.22
Discontinued operations	$0	$0	$0	$0.14
Net income (loss)	$0.01	$0.36	($0.44)	$0.36
Diluted net income (loss) per share from:	'	'	'	'
Continuing operations	$0.01	$0.36	($0.44)	$0.22
Discontinued operations	$0	$0	$0	$0.14
Net income (loss)	$0.01	$0.36	($0.44)	$0.36
Shares used in per share calculation:	'	'	'	'
Basic	90,618	101,144	94,113	108,695
Diluted	91,800	102,723	94,113	109,879

CONDENSED_CONSOLIDATED_STATEME1

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Income Statement [Abstract]	'	'
Gain on disposal, net of taxes	$0	$14,813

CONDENSED_CONSOLIDATED_STATEME2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Net income (loss)	$1,078	$36,766	($41,394)	$39,387
Other comprehensive income (loss), net of tax:	'	'	'	'
Foreign currency translation adjustments	-670	462	-440	-8
Gain (loss) on investments	-308	52	-333	11
Other comprehensive income (loss) before tax	-978	514	-773	3
Income tax expense (benefit) related to items of other comprehensive income (loss)	-7	17	-12	5
Other comprehensive income (loss), net of tax	-971	497	-761	-2
Comprehensive income (loss)	$107	$37,263	($42,155)	$39,385

CONDENSED_CONSOLIDATED_STATEME3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Cash flows from operating activities:	'	'
Net income (loss)	($41,394)	$39,387
Adjustments to reconcile net income (loss) to net cash provided by operating activities:	'	'
Amortization of intangibles	18,378	20,569
Depreciation	12,641	12,365
Stock-based compensation	12,720	11,953
Gain on sale of discontinued operations, net of tax	0	-14,813
Loss on impairment of fixed assets	0	149
Deferred income taxes	31,782	-10,647
Provision for excess and obsolete inventories	2,013	2,813
Allowance for doubtful accounts, returns and discounts	-116	1,161
Excess tax benefits from stock-based compensation	-194	0
Other non-cash adjustments, net	1,108	1,220
Changes in assets and liabilities:	'	'
Accounts receivable	-472	-310
Inventories	2,401	10,509
Prepaid expenses and other assets	-5,321	8,522
Accounts payable	-786	-5,418
Deferred revenue	7,770	5,127
Income taxes payable	-8,292	-39,209
Accrued and other liabilities	-4,717	-8,244
Net cash provided by operating activities	27,521	35,134
Cash flows from investing activities:	'	'
Purchases of investments	-26,599	-54,773
Proceeds from maturities of investments	43,236	50,681
Proceeds from sales of investments	7,408	31,506
Purchases of property and equipment	-8,859	-11,249
Purchases of long-term investments	-5,867	0
Proceeds from sale of discontinued operations, net of selling costs	0	43,527
Net cash provided by investing activities	9,319	59,692
Cash flows from financing activities:	'	'
Payments for repurchase of common stock	-86,407	-103,496
Proceeds from common stock issued to employees	1,241	5,355
Excess tax benefits from stock-based compensation	194	0
Net cash used in financing activities	-84,972	-98,141
Effect of exchange rate changes on cash and cash equivalents	-169	-25
Net decrease in cash and cash equivalents	-48,301	-3,340
Cash and cash equivalents at beginning of period	90,329	96,670
Cash and cash equivalents at end of period	$42,028	$93,330

Basis_of_Presentation_and_Sign

Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 26, 2014
Accounting Policies [Abstract]	'
Basis of Presentation and Significant Accounting Policies	'
	BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES
	Basis of Presentation
	The accompanying unaudited condensed consolidated financial statements, in the opinion of management, include all adjustments (consisting only of normal recurring adjustments) which Harmonic Inc. (“Harmonic,” or the “Company”) considers necessary for a fair statement of the results of operations for the interim periods covered and the consolidated financial condition of the Company at the date of the balance sheets. This Quarterly Report on Form 10-Q should be read in conjunction with the Company’s audited consolidated financial statements contained in the Company’s Annual Report on Form 10-K, which was filed with the Securities and Exchange Commission on February 28, 2014 (“2013 Form 10-K”). The interim results presented herein are not necessarily indicative of the results of operations that may be expected for the full fiscal year ending December 31, 2014, or any other future period. The Company’s fiscal quarters are based on 13-week periods, except for the fourth quarter, which ends on December 31.
	The condensed consolidated financial statements include the accounts of the Company and its subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation. The year-end condensed balance sheet was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America (“US GAAP”).
	Discontinued Operations
	In the first quarter of fiscal 2013, the Company completed the sale of its cable access hybrid-fiber coaxial ("HFC") business to Aurora Networks (“Aurora”). The results of operations associated with the cable access HFC business were presented as discontinued operations in its unaudited condensed consolidated financial statements as described in Note 3, "Discontinued Operations". There were no operating activities associated with the cable access HFC business after December 31, 2013. Unless noted otherwise, all discussions herein with respect to the Company’s unaudited condensed consolidated financial statements relate to the Company’s continuing operations.
	Use of Estimates
	The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates.
	Variable Interest Entities
	From time to time, the Company may enter into investments in entities that are considered variable interest entities under Accounting Standards Codification (ASC) Topic 810. If the Company is the primary beneficiary of a variable interest entity ("VIE"), it is required to consolidate it. To determine if the Company is the primary beneficiary of a VIE, the Company evaluates whether it has (1) the power to direct the activities that most significantly impact the VIE's economic performance, and (2) the obligation to absorb losses or the right to receive benefits from the VIE that could potentially be significant to the VIE. The assessment of whether the Company is the primary beneficiary of its VIE requires significant assumptions and judgments.
	Investments in Equity Securities
	The Company accounts for its investments in entities that it does not have significant influence under the cost method. Investments in equity securities are carried at fair value if the fair value of the security is readily determinable. Equity investments carried at fair value are classified as long-term investments and included in "Other assets" in the Company's Condensed Consolidated Balance Sheet. Unrealized gains and losses, net of taxes, on the long-term investments are included in the Company's Condensed Consolidated Balance Sheet as a component of accumulated other comprehensive income (loss). Investments in equity securities that do not qualify for fair value accounting or equity method accounting are accounted for under the cost method. In accordance with the cost method, the Company's initial investment is recorded at cost and the Company reviews all of its cost method investments quarterly to determine if impairment indicators exist. Cost method investments are classified as long-term investments and included in "Other assets" in the Company's Condensed Consolidated Balance Sheet.
	Segment Reporting
	The Company operates its business in one reportable segment, which is the design, manufacture and sale of versatile and high performance video infrastructure products and system solutions. Operating segments are defined as components of an enterprise that engage in business activities for which separate financial information is available and evaluated by the chief operating decision  maker (which for Harmonic is the Chief Executive Officer) in deciding how to allocate resources and assess performance. More recently, the Company has started to view its business through two market segments: Video and Cable Edge. As part of its annual year-end financial planning process, the Company expects to develop internal processes, policies and controls to enable timely and reliable measuring of operating profits by these segments. The Company expects the chief operating decision maker will apply this information in deciding how to allocate resources and assess the Company's performance. As such, the Company anticipates reporting the operating results for the Video and Cable Edge business in its segment reporting in the fourth quarter of 2014.
	Significant Accounting Policies
	The Company’s significant accounting policies are described in Note 2 to its audited Consolidated Financial Statements included in its 2013 Form 10-K. There have been no significant changes to these policies during the nine months ended September 26, 2014.

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	9 Months Ended
	Sep. 26, 2014
Accounting Changes and Error Corrections [Abstract]	'
Recent Accounting Pronouncements	'
	RECENT ACCOUNTING PRONOUNCEMENTS
	In March 2013, the FASB issued ASU 2013-05, “Parent’s Accounting for the Cumulative Translation Adjustment upon De-recognition of Certain Subsidiaries or Groups of Assets within a Foreign Entity or of an Investment in a Foreign Entity”. The ASU addresses accounting for a cumulative translation adjustment when a parent either sells a part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or group of assets that is a nonprofit activity or a business within a foreign entity. The new guidance became effective for the Company beginning in the first quarter of fiscal 2014 and it did not have a material impact on the Company’s Consolidated Financial Statements.
	In July 2013, the FASB issued ASU 2013-11, “Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists”. Under certain circumstances, unrecognized tax benefits should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward. The new guidance became effective for the Company beginning in the first quarter of fiscal 2014 and it did not have a material impact on the Company’s Consolidated Financial Statements.
	On April 10, 2014, the FASB issued ASU 2014-08, “Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity". This guidance raises the threshold for a disposal to qualify as a discontinued operation and requires new disclosures of both discontinued operations and certain other disposals that do not meet the definition of a discontinued operation. The guidance is effective for the Company beginning in the first quarter of fiscal 2015. The Company does not expect the adoption of ASU 2014-08 will have a material impact on its financial position, results of operations or cash flows.
	On May 28, 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers", requiring an entity to recognize the amount of revenue that reflects the consideration to which it expects to be entitled for the transfer of promised goods or services to customers. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective and permits the use of either the retrospective or cumulative effect transition method. Early adoption is not permitted. The updated standard becomes effective for the Company in the first quarter of fiscal 2017. We have not yet selected a transition method and we are currently evaluating the effect that the updated standard will have on our consolidated financial statements and related disclosures.

Discontinued_Operations

Discontinued Operations	9 Months Ended
	Sep. 26, 2014
Discontinued Operations and Disposal Groups [Abstract]	'
Discontinued Operations	'
	DISCONTINUED OPERATIONS
	In February 2013, the Company entered into an Asset Purchase Agreement with Aurora pursuant to which the Company agreed to sell its cable access HFC business for $46.0 million in cash. On March 5, 2013, the sale transaction closed and the Company received gross proceeds of $46.0 million from the sale and recorded a net gain of $15.0 million in connection with the sale in the first quarter of fiscal 2013, adjusted by ($0.2) million in the second quarter of fiscal 2013, primarily related to adjustments on inventory and fixed assets sold to Aurora, for a net gain of $14.8 million. The gain was included in income from discontinued operations, net of tax in the Condensed Consolidated Statement of Operations for the nine months ended September 27, 2013.
	In March 2013, the Company entered into a transition services agreement (‘TSA”) with Aurora to provide contract manufacturing and other various support, including providing order fulfillment, taking warranty calls, attending to product returns from customers, providing cost accounting analysis, receiving payments from customers and remitting such payments to Aurora. The TSA fees were a fixed amount per month and were determined based on the Company’s estimated cost of delivering the transition services. In addition, in April 2013, the Company and Aurora signed a sublease agreement for the Company’s Milpitas warehouse for the remaining period of the lease.
	The TSA ended in October 2013 and the billing to Aurora was recorded in the Condensed Consolidated Statements of Operations under income from continuing operations as an offset to the expenses incurred to deliver the transition services. The table below provides details on the income statement caption under which the TSA billing was recorded (in thousands):
		Three months ended			Nine months ended
		27-Sep-13
	Product cost of revenue	$	41		$	577
	Research and development	—			21
	Selling, general and administrative	7			379
	Total TSA billing to Aurora	$	48		$	977
	The Company recorded a gain of $14.8 million in the nine months ended September 27, 2013 , in connection with the sale of the cable access HFC business, calculated as follows (in thousands):
	Gross Proceeds				$	46,000
	Less : Carrying value of net assets
	Inventories, net	$	10,579
	Prepaid expenses and other current assets	612
	Property and equipment, net	1,180
	Goodwill de-recognized	14,547
	Deferred revenue	(4,499		)
	Accrued liabilities	(939		)
	Total net assets sold and de-recognized				$	21,480
	Less : Selling cost				2,473
	Less : Tax effect				7,234
	Gain on disposal, net of taxes				$	14,813
	Since the Company has one reporting unit, upon the sale of the cable access HFC business, approximately $14.5 million of the carrying value of goodwill was allocated to the cable access HFC business based on the relative fair value of the cable access HFC business to the fair value of the Company. The remaining carrying value of goodwill was tested for impairment, and the Company determined that goodwill was not impaired as of March 29, 2013.
	The results of operations associated with the cable access HFC business are presented as discontinued operations in the Company’s Condensed Consolidated Statements of Operations for fiscal 2013. There were no operating activities associated with the cable access HFC business after December 31, 2013. Revenue and the components of net income related to the discontinued operations for the three and nine months ended September 27, 2013 were as follows (in thousands):
		Three months ended			Nine months ended
		27-Sep-13
	Revenue	$	161		$	9,717
	Operating income	$	154		$	669
	Less : Provision for (benefit from) income taxes	57			(137		)
	Add : Gain (loss) on disposal, net of taxes	(6		)	14,813
	Income from discontinued operations, net of taxes	$	91		$	15,619

Investments_in_Equity_Securiti

Investments in Equity Securities Investments in Equity Securities	9 Months Ended
	Sep. 26, 2014
Investments, All Other Investments [Abstract]	'
Investments in Equity Securities	'
	INVESTMENTS IN EQUITY SECURITIES
	On September 26, 2014, the Company acquired a 19.8% interest in VJU iTV Development GmbH ("VJU"), a software company based in Austria, for $2.5 million. Since VJU's equity is deemed not sufficient to permit it to finance its activities without additional support from its shareholders, VJU is considered a variable interest entity ("VIE"). The Company determined that it is not the primary beneficiary of VJU because its financial interest in VJU's equity and its research and development agreement with VJU do not empower the Company to direct VJU's activities that will most significantly impact VJU's economic performance. VJU is accounted for as a cost method investment as the Company does not have significant influence over the operational and financial policies of VJU. As of September 26, 2014, the carrying value of VJU was $2.5 million and it is included in “Other assets" in the Condensed Consolidated Balance Sheet. As of September 26, 2014, the Company's maximum exposure to loss from investment in VJU was limited to the investment cost and research and development fees paid to VJU in the amount of $2.5 million and $0.1 million, respectively.
	On September 2, 2014, the Company acquired a 3.3% interest in Vislink plc ("Vislink"), a U.K. public company listed on the AIM exchange, for $3.3 million, and also made $3.3 million prepayment for future software license purchases. The investment in Vislink is being accounted for as a cost method investment as the Company does not have significant influence over the operational and financial policies of Vislink. The Vislink investment is marked to market for the difference in fair value at period end, and as of September 26, 2014, the carrying value of Vislink was $3.1 million and is included in “Other assets" in the Condensed Consolidated Balance Sheet. The $3.3 million prepayment for future software license purchases is included in "Prepaid expenses and other current assets" in the Condensed Consolidated Balance Sheet.
	The Company reviews all of its cost method investments quarterly to determine if impairment indicators exist.

ShortTerm_Investments

Short-Term Investments	9 Months Ended
	Sep. 26, 2014
Cash and Cash Equivalents [Abstract]	'
Short-Term Investments	'
	SHORT-TERM INVESTMENTS
	The following table summarizes the Company’s short-term investments (in thousands):
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	As of September 26, 2014
	State, municipal and local government agencies bonds	$	25,719	$	26	$	(31	)	$	25,714
	Corporate bonds	26,150		5		(17		)	26,138
	Commercial paper	3,299		—		—			3,299
	U.S. federal government bonds	—		—		—			—
	Total short-term investments	$	55,168	$	31	$	(48	)	$	55,151
	As of December 31, 2013
	State, municipal and local government agencies bonds	$	40,426	$	38	$	(15	)	$	40,449
	Corporate bonds	33,483		20		(7		)	33,496
	Commercial paper	2,299		—		—			2,299
	U.S. federal government bonds	4,004		4		—			4,008
	Total short-term investments	$	80,212	$	62	$	(22	)	$	80,252
	The following table summarizes the maturities of the Company’s short-term investments (in thousands):
		26-Sep-14		31-Dec-13
	Less than one year	$	44,452	$	55,278
	Due in 1 - 2 years	10,699		24,974
	Total short-term investments	$	55,151	$	80,252
	These available-for-sale investments are presented as Current Assets as they are available for current operations. Realized gains and losses from the sale of investments for the three and nine months ended September 26, 2014 and September 27, 2013 were not material.
	Impairment of Investments
	The Company monitors its investment portfolio for impairment on a periodic basis. In the event that the carrying value of an investment exceeds its fair value and the decline in value is determined to be other-than-temporary, an impairment charge is recorded and a new cost basis for the investment is established. A decline of fair value below amortized costs of debt securities is considered other-than-temporary if the Company has the intent to sell the security or it is more likely than not that the Company will be required to sell the security before recovery of the entire amortized cost basis. At the present time, the Company does not intend to sell its investments that have unrealized losses in accumulated other comprehensive loss. In addition, the Company does not believe that it is more likely than not that it will be required to sell its investments that have unrealized losses in accumulated other comprehensive loss before the Company recovers the principal amounts invested. The Company believes that the unrealized losses are temporary and do not require an other-than-temporary impairment, based on its evaluation of available evidence as of September 26, 2014.
	As of September 26, 2014, there were no individual available-for-sale securities in a material unrealized loss position and the amount of unrealized losses on the total investment balance was insignificant.

Derivative_and_Hedgiing_Activi

Derivative and Hedgiing Activities Derivative and Hedging Activities	9 Months Ended
	Sep. 26, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Instruments and Hedging Activities Disclosure	'
	DERIVATIVES AND HEDGING ACTIVITIES
	The Company enters into foreign currency forward contracts to minimize the short-term impact of foreign currency exchange rate fluctuations on cash and certain trade and inter-company receivables and payables, primarily denominated in Euro, British pound, Japanese yen and Israeli shekel. These contracts reduce the exposure to fluctuations in foreign currency exchange rate movements as the gains and losses associated with foreign currency balances are generally offset with the gains and losses on the forward contracts. These contracts are not designated as hedges that are eligible for hedge accounting treatment and are marked to market through earnings every period and generally range from one to three months in original maturity. The Company does not enter into foreign currency forward contacts for trading purposes. The balance sheet location and net fair value of each of the Company’s derivatives are as follows (in thousands):
				Fair Value of Asset (Liability)
	Derivatives not designated as hedging instruments	Balance Sheet Location		26-Sep-14				31-Dec-13
	Foreign currency contracts	Prepaid expenses and other current assets		$	19			$	196
	Foreign currency contracts	Accrued liabilities		(331		)		(195		)
	The effects of the changes in the fair values of non-designated foreign currency forward contracts are summarized as follows (in thousands) :
		Three Months Ended								Nine months ended
		26-Sep-14				27-Sep-13				26-Sep-14			27-Sep-13
	Gain (loss) recorded in other income (expense), net	$	(95	)		$	(157	)		$	(201	)	$	658

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 26, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	FAIR VALUE MEASUREMENTS
	The applicable accounting guidance establishes a framework for measuring fair value and requires disclosure about the fair value measurements of assets and liabilities. This guidance requires the Company to classify and disclose assets and liabilities measured at fair value on a recurring basis, as well as fair value measurements of assets and liabilities measured on a nonrecurring basis in periods subsequent to initial measurement, in a three-tier fair value hierarchy as described below.
	The guidance defines fair value as the exchange price that would be received for an asset or paid to transfer a liability, in the principal or most advantageous market for the asset or liability, in an orderly transaction between market participants on the measurement date.
	Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The guidance describes three levels of inputs that may be used to measure fair value:
	•	Level 1 — Observable inputs that reflect quoted prices for identical assets or liabilities in active markets.
	•	Level 2 — Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. The Company primarily uses broker quotes for valuation of its short-term investments. The forward exchange contracts are classified as Level 2 because they are valued using quoted market prices and other observable data for similar instruments in an active market.
	•	Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
	The Company uses the market approach to measure fair value for its financial assets and liabilities. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities. During the nine months ended September 26, 2014, there were no nonrecurring fair value measurements of assets and liabilities subsequent to initial recognition.
	The following table sets forth the fair value of the Company’s financial assets and liabilities measured at fair value based on the three-tier fair value hierarchy (in thousands):
		Level 1		Level 2		Level 3		Total
	As of September 26, 2014
	Cash equivalents
	Money market funds	$	4,292	$	—	$	—	$	4,292
	Short-term investments
	State, municipal and local government agencies bonds	—		25,714		—		25,714
	Corporate bonds	—		26,138		—		26,138
	Commercial paper	—		3,299		—		3,299
	U.S. federal government bonds			—		—		—
	Prepaids and other current assets
	Derivative assets (1)	—		19		—		19
	Other assets
	Long-term investment	3,101						3,101
	Total assets measured and recorded at fair value	$	7,393	$	55,170	$	—	$	62,563
	Accrued liabilities
	Derivative liabilities (1)	$	—	$	331	$	—	$	331
	Total liabilities measured and recorded at fair value	$	—	$	331	$	—	$	331
		Level 1		Level 2		Level 3		Total
	As of December 31, 2013
	Cash equivalents
	Money market funds	$	51,014	$	—	$	—	$	51,014
	Short-term investments
	State, municipal and local government agencies bonds	—		40,449		—		40,449
	Corporate bonds	—		33,496		—		33,496
	Commercial paper	—		2,299		—		2,299
	U.S. federal government bonds	4,008		—		—		4,008
	Prepaids and other current assets
	Derivative assets (1)	—		196		—		196
	Total assets measured and recorded at fair value	$	55,022	$	76,440	$	—	$	131,462
	Accrued liabilities
	Derivative liabilities (1)	$	—	$	195	$	—	$	195
	Total liabilities measured and recorded at fair value	$	—	$	195	$	—	$	195
	(1) Derivative assets and liabilities represent forward currency exchange contracts. The Company enters into these contracts to minimize the short-term impact of foreign currency exchange rates fluctuations primarily from trade and inter-company receivables and payables.

Balance_Sheet_Components

Balance Sheet Components	9 Months Ended
	Sep. 26, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Balance Sheet Components	'
	BALANCE SHEET COMPONENTS
	The following tables provide details of selected balance sheet components (in thousands):
		26-Sep-14			31-Dec-13
	Accounts receivable, net:
	Accounts receivable	$	81,988		$	83,266
	Less: allowances for doubtful accounts, returns and discounts	(6,348		)	(8,214		)
	Accounts receivable, net	$	75,640		$	75,052
	Inventories:
	Raw materials	$	1,805		$	2,389
	Work-in-process	1,780			976
	Finished goods	28,927			33,561
		$	32,512		$	36,926
	Property and equipment, net:
	Furniture and fixtures	$	8,796		$	8,227
	Machinery and equipment	117,765			114,178
	Leasehold improvements	8,386			7,888
	Property and equipment, gross	134,947			130,293
	Less: accumulated depreciation and amortization	(104,133		)	(95,348		)
		$	30,814		$	34,945

Goodwill_and_Identified_Intang

Goodwill and Identified Intangible Assets	9 Months Ended
	Sep. 26, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Goodwill and Identified Intangible Assets	'
	GOODWILL AND IDENTIFIED INTANGIBLE ASSETS
	The changes in the carrying amount of goodwill for the nine months ended September 26, 2014 are as follows (in thousands):
	Balance at beginning of period	$	198,022
	Foreign currency translation adjustment	(15		)
	Balance at end of period	$	198,007
	The following is a summary of identified intangible assets (in thousands):
				26-Sep-14												31-Dec-13
		Range of Useful Lives		Gross Carrying				Accumulated				Net Carrying				Gross Carrying		Accumulated			Net Carrying
				Amount				Amortization				Amount				Amount		Amortization			Amount
	Identifiable intangibles:
	Developed core technology	4-6 years		$	136,145			$	(134,731	)		$	1,414			$	136,145	$	(121,681	)	$	14,464
	Customer relationships/contracts	5-6 years		67,098				(57,568		)		9,530				67,098		(53,772		)	13,326
	Trademarks and tradenames	4-5 years		11,361				(11,361		)		—				11,361		(10,565		)	796
	Maintenance agreements and related relationships	6-7 years		7,100				(5,304		)		1,796				7,100		(4,567		)	2,533
	Total identifiable intangibles			$	221,704			$	(208,964	)		$	12,740			$	221,704	$	(190,585	)	$	31,119
	Amortization expense for the identifiable purchased intangible assets for the three and nine months ended September 26, 2014 and September 27, 2013 was allocated as follows (in thousands):
		Three months ended								Nine months ended
		September 26,				September 27,				September 26,				September 27,
		2014				2013				2014				2013
	Included in cost of revenue	$	3,851			$	4,763			$	13,049			$	14,470
	Included in operating expenses	1,661				2,001				5,329				6,099
	Total amortization expense	$	5,512			$	6,764			$	18,378			$	20,569
	The estimated future amortization expense of purchased intangible assets with definite lives is as follows (in thousands):
		Cost of Revenue				Operating				Total
						Expenses
	Year ended December 31,
	2014 (remaining 3 months)	$	695			$	1,446			$	2,141
	2015	719				5,783				6,502
	2016	—				4,097				4,097
	Total future amortization expense	$	1,414			$	11,326			$	12,740

Restructuring_and_Related_Char

Restructuring and Related Charges	9 Months Ended
	Sep. 26, 2014
Restructuring and Related Activities [Abstract]	'
Restructuring and Related Charges	'
	RESTRUCTURING AND RELATED CHARGES
	The Company accounts for its restructuring plans under the authoritative guidance for exit or disposal activities. The restructuring and related charges are included in “Product cost of revenue” and "Operating expenses-restructuring and related charges” in the Condensed Consolidated Statements of Operations. The following table summarizes the restructuring and related charges (in thousands):
		Three months ended					Nine months ended
		September 26,			September 27,		September 26,			September 27,
		2014			2013		2014			2013
	Restructuring and related charges in:
	Product cost of revenue	$	15		$	324	$	94		$	530
	Operating expenses-Restructuring and related charges	388			259		821			925
		$	403		$	583	$	915		$	1,455
	Harmonic 2013 Restructuring
	In the first quarter of fiscal 2013, the Company committed to a restructuring plan to reduce costs and improve efficiencies. This restructuring plan extended to actions taken through fiscal 2014. In fiscal 2013, the Company recorded $2.2 million of restructuring charges under this plan consisting of worldwide workforce reductions, writing down leasehold improvements and furniture related to its Milpitas warehouse to estimated net realizable value, and obsolete inventory at its Israel facilities. Of the $2.2 million restructuring charges in fiscal 2013, $1.5 million was recorded in the nine months ended September 27, 2013. For a complete discussion of the restructuring actions related to the 2013 restructuring plan, please refer to Note 9 of the Notes to Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2013.
	The Company recorded restructuring charges of $403,000 and $915,000 under this plan, in the three and nine months ended September 26, 2014, respectively. The restructuring charges in the nine months ended September 26, 2014 consisted of severance and benefits related to the termination of twenty-five employees worldwide, costs associated with exiting from a research and development project, as well as costs associated with vacating from an excess facility in France. The following table summarizes the activity in the restructuring accrual under this plan during the nine months ended September 26, 2014 (in thousands):
		Severance			Termination of a research & development project		Excess facilities			Total
	Balance at December 31, 2013	$	179		$	—	$	—		$	179
	2013 Plan restructuring charges	829			63		32			924
	Adjustments to restructuring provisions	(9		)	—		—			(9		)
	Cash payments	(715		)	—		(32		)	(747		)
	Balance at September 26, 2014	$	284		63		$	—		$	347
	The Company anticipates that the remaining restructuring accrual balance of $347,000 will be substantially paid out by the end of the fourth quarter of fiscal 2014.
	HFC Restructuring
	As a result of the sale of the cable access HFC business in March 2013, the Company recorded $600,000 of restructuring charges under "Income from discontinued operations" in fiscal 2013 consisting of severance and benefits and contract termination costs. For a complete discussion of the restructuring actions related to the HFC restructuring plan, please refer to Note 9 of the Notes to Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2013.
	The remaining restructuring accrual balance of $13,000 as of December 31, 2013 was fully paid in the first quarter of fiscal 2014.

Credit_Facilities

Credit Facilities	9 Months Ended
	Sep. 26, 2014
Debt Disclosure [Abstract]	'
Credit Facilities	'
	CREDIT FACILITIES
	Harmonic has a bank line of credit facility with Silicon Valley Bank that provides for borrowings of up to $10.0 million and matures on December 31, 2014. This facility, which became effective in August 2011 and was amended in August 2012, and further amended in August 2013, contains a financial covenant that requires Harmonic to maintain a ratio of unrestricted cash, accounts receivable and short term investments to current liabilities (less deferred revenue) of at least 1.75 to 1.00. On August 22, 2014, a third amendment was made to extend the maturity date to December 31, 2014 and the LIBOR margin was reduced from 1.75% to 1.50%.
	There were no borrowings during the nine months ended September 26, 2014. As of September 26, 2014, the amount available for borrowing under this facility, net of $0.2 million of standby letters of credit, was $9.8 million.
	As of September 26, 2014, the Company’s ratio under that covenant was 3.26 to 1. In the event of noncompliance by Harmonic with the covenants under the facility, including the financial covenant referenced above, Silicon Valley Bank would be entitled to exercise its remedies under the facility, including declaring all obligations immediately due and payable. As of September 26, 2014, Harmonic was in compliance with the covenants under the line of credit facility. Borrowings pursuant to the line would bear interest at the bank’s prime rate (3.25% at September 26, 2014,) or at LIBOR for the desired borrowing period (an annualized rate of 0.15% for a one month borrowing period at September 26, 2014) plus 1.50%, or 1.65%. Borrowings are not collateralized.

Employee_Benefit_Plans

Employee Benefit Plans	9 Months Ended
	Sep. 26, 2014
Postemployment Benefits [Abstract]	'
Employee Benefit Plans	'
	EMPLOYEE BENEFIT PLANS
	Harmonic grants stock options and restricted stock units (“RSUs”) pursuant to stockholder approved equity incentive plans. These equity incentive plans are described in detail in Note 12, “Employee Benefit Plans”, of Notes to Consolidated Financial Statements in the 2013 Form 10-K.
	Stock Options and Restricted Stock Units
	The following table summarizes the Company’s stock option and RSU unit activity during the nine months ended September 26, 2014 (in thousands, except per share amounts):
				Stock Options Outstanding						Restricted Stock Units Outstanding
		Shares		Number			Weighted			Number		Weighted
		Available for		of			Average			of		Average
		Grant		Shares			Exercise Price			Units		Grant
												Date Fair
												Value
	Balance at December 31, 2013	8,752		7,885			$	6.92		3,018		$	6.34
	Authorized	350		—			—			—		—
	Granted	(3,477	)	1,450			6.52			1,352		6.55
	Options exercised	—		(329	)		4.91			—		—
	Shares released	—		—			—			(1,589	)	6.32
	Forfeited or cancelled	1,753		(1,592	)		8.15			(232	)	6.13
	Balance at September 26, 2014	7,378		7,414			$	6.67		2,549		$	6.49
	The following table summarizes information about stock options outstanding as of September 26, 2014 (in thousands, except per share amounts):
		Number		Weighted				Weighted	Aggregate
		of		Average				Average	Intrinsic
		Shares		Exercise				Remaining	Value
				Price				Contractual
								Term (Years)
	Vested and expected to vest	7,095		$	6.68			3.6	$	3,118
	Exercisable	4,760		6.84				2.5	2,519
	The intrinsic value of options vested and expected to vest and exercisable as of September 26, 2014 is calculated based on the difference between the exercise price and the fair value of the Company’s common stock as of September 26, 2014. The intrinsic value of options exercised is calculated based on the difference between the exercise price and the fair value of the Company's common stock as of the exercise date. The intrinsic value of options exercised during the three and nine months ended September 26, 2014 was $0.3 million and $0.7 million, respectively. The intrinsic value of options exercised during the three and nine months ended September 27, 2013 was $1.1 million and $2.0 million, respectively.
	The following table summarizes information about restricted stock units outstanding as of September 26, 2014 (in thousands, except per share amounts):
		Number of		Weighted		Aggregate
		Shares		Average		Fair
		Underlying		Remaining		Value
		Restricted		Vesting
		Stock		Period
		Units		(Years)
	Vested and expected to vest	2,365		0.7		$	15,114
	The fair value of restricted stock units vested and expected to vest as of September 26, 2014 is calculated based on the fair value of the Company's common stock as of September 26, 2014.
	Employee Stock Purchase Plan
	The 2002 Employee Stock Purchase Plan (“ESPP”) provides for the issuance of common stock purchase rights to employees of the Company. The ESPP is intended to qualify as an “employee stock purchase plan” under Section 423 of the Internal Revenue Code. The ESPP enables employees to purchase shares at 85% of the fair market value of the common stock at the beginning or end of the offering period, whichever is lower. Offering periods generally begin on the first trading day on or after January 1 and July 1 of each year. Employees may participate through payroll deductions of 1% to 10% of their earnings. In the event that there are insufficient shares in the plan to fully fund the issuance, the available shares will be allocated across all participants based on their contributions relative to the total contributions received for the offering period.
	There was a shortage of approved shares in the ESPP to fund the total employee contributions from January 2, 2013 to June 30, 2013. The shares available in the plan were sufficient to fund approximately 53% of the total contributions. As a result, the shares available were issued ratably to the participants based on each of their contributions during the offering period, relative to the total contributions received from all participants. The participants were refunded the remaining 47% of their contributions and the ESPP was suspended for the second half of 2013. The Company’s stockholders approved a 1,000,000 share increase in the authorized shares for the ESPP during the Company’s annual meeting on August 14, 2013, and contributions under the ESPP resumed in January 2014. In anticipation of another potential future shortfall of approved shares in the ESPP, the Company’s stockholders approved an additional 1,000,000 share increase in the authorized shares for the ESPP during the Company’s annual meeting on July 29, 2014.
	401(k) Plan
	Harmonic has a retirement/savings plan which qualifies as a thrift plan under Section 401(k) of the Internal Revenue Code. This plan allows participants to contribute up to the applicable Internal Revenue Code limitations under the plan. Harmonic has made discretionary contributions to the plan of 25% of the first 4% contributed by eligible participants, up to a maximum contribution per participant of $1,000 per year. Harmonic contributed $354,000 and $387,000 for the nine months ended September 26, 2014 and September 27, 2013, respectively.

StockBased_Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 26, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Stock-Based Compensation	'
	STOCK-BASED COMPENSATION
	Stock-based compensation expense consists primarily of expenses for stock options and restricted stock units granted to employees and shares issued under the ESPP. The following table summarizes stock-based compensation expense (in thousands):
		Three months ended							Nine months ended
		September 26,			September 27,				September 26,			September 27,
		2014			2013				2014			2013
	Stock-based compensation in:
	Cost of revenue	$	612		$	605			$	1,751		$	1,838
	Research and development expense	1,219			1,076				3,589			3,400
	Selling, general and administrative expense	2,521			2,264				7,380			6,628
	Total stock-based compensation in operating expense	3,740			3,340				10,969			10,028
	Total stock-based compensation	$	4,352		$	3,945			$	12,720		$	11,866
	Stock Options
	The Company estimated the fair value of all employee stock options using a Black-Scholes valuation model with the following weighted average assumptions:
		Three months ended					Nine months ended
		September 26,		September 27,			September 26,			September 27,
		2014		2013			2014			2013
	Expected term (years)	4.7		4.7			4.7			4.7
	Volatility	40	%	46	%		40	%		51	%
	Risk-free interest rate	1.8	%	1.5	%		1.7	%		0.8	%
	Expected dividends	0	%	0	%		0	%		0	%
	The expected term represents the weighted-average period that the stock options are expected to remain outstanding. The computation of the expected term was determined based on historical experience of similar awards, giving consideration to the contractual terms of the stock-based awards, vesting schedules and expectations of future employee behavior. The Company uses its historical volatility for a period equivalent to the expected term of the options to estimate the expected volatility. The risk-free interest rate that the Company uses in the Black-Scholes option valuation model is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected term. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future, and, therefore, used an expected dividend yield of zero in the valuation model.
	The Company is required to estimate forfeitures at the time of grant and revise those estimates in subsequent periods if actual forfeitures differ from those estimates. The Company uses historical data to estimate pre-vesting option forfeitures and records stock-based compensation expense only for those awards that are expected to vest. All stock-based payment awards are amortized on a straight-line basis over the requisite service periods of the awards, which are generally the vesting periods.
	The weighted-average fair value per share of options granted was $2.48 and $3.02 for the three months ended September 26, 2014 and September 27, 2013, respectively. The weighted-average fair value per share of options granted was $2.36 and $2.51 for the nine months ended September 26, 2014 and September 27, 2013, respectively.
	The fair value of all stock options vested during the three months ended September 26, 2014 and September 27, 2013 was $0.6 million and $0.8 million respectively. The fair value of all stock options vested during the nine months ended September 26, 2014 and September 27, 2013 was $2.6 million and $2.8 million respectively.
	The total realized tax benefit attributable to stock options exercised during the nine months ended September 26, 2014, in jurisdictions where this expense is deductible for tax purposes, was $194,000. The Company did not recognize any tax benefit attributable to stock options exercised during the nine months ended September 27, 2013.
	Restricted Stock Units
	The aggregate fair value of all restricted stock units issued during the three months ended September 26, 2014 and September 27, 2013 was $2.7 million and $2.8 million respectively. The estimated fair value of all restricted stock units issued during the nine months ended September 26, 2014 and September 27, 2013 were $10.0 million and $10.2 million respectively.
	Employee Stock Purchase Plan
	The value of the stock purchase rights under the ESPP consists of: (1) the 15% discount on the purchase of the stock; (2) 85% of the fair value of the call option; and (3) 15% of the fair value of the put option. The call option and put option were valued using the Black-Scholes option pricing model. The weighted average fair value of the Company's ESPP shares at purchase dates was estimated using the following weighted average assumptions during the nine months ended September 26, 2014 and September 27, 2013:
		Purchase Period Ending
		December 31,		June 30,			June 30,
		2014		2014			2013
	Expected term (years)	0.5		0.5			0.49
	Volatility	33	%	28	%		30	%
	Risk-free interest rate	0.1	%	0.1	%		0.2	%
	Expected dividends	0	%	0	%		0	%
	Estimated weighted average fair value per share at purchase date	$1.84		$1.70			$1.23
	The expected term represents the period of time from the beginning of the offering period to the purchase date. The Company uses its historical volatility for a period equivalent to the expected term of the options to estimate the expected volatility. The risk-free interest rate that the Company uses in the Black-Scholes option valuation model is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected term. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future, and, therefore, used an expected dividend yield of zero in the valuation model.
	The ESPP was suspended for the second half of 2013 due to all authorized shares under the plan having been issued through the offering period ended June 30, 2013. The Company’s stockholders approved a 1,000,000 share increase in the authorized shares for the ESPP during the Company’s annual meeting on August 14, 2013, and contributions under the ESPP resumed in January 2014. As a result, the Company did not have any stock-based compensation expense in the second half of fiscal 2013 related to the ESPP.
	Unrecognized Stock-Based Compensation
	As of September 26, 2014, total unamortized stock-based compensation cost related to unvested stock options and restricted stock units was $17.1 million. This amount will be recognized as expense using the straight-line attribution method over the remaining weighted-average vesting period of 1.7 years.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 26, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	INCOME TAXES
	The Company reported the following operating results for the periods presented (in thousands):
		Three months ended						Nine months ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
	Loss from continuing operations before income taxes	$	(3,752	)	$	(2,278	)	$	(19,594	)	$	(21,955	)
	Provision for (benefit from) income taxes	(4,830		)	(38,953		)	21,800			(45,723		)
	Effective income tax rate	128.7		%	1,710.00		%	(111.3		)%	208.3		%
	The Company's quarterly income taxes reflect an estimate of the corresponding fiscal year's annual effective tax rate and include, where applicable, adjustments for discrete tax items.
	The Company's effective rate for the nine months ended September 26, 2014 was different from the U.S. federal statutory rate of 35%, primarily due to a $28.7 million increase in the valuation allowance against both U.S. federal, California and other state deferred tax assets, as a result of a history of operating losses in recent years that has led to uncertainty with respect to the Company’s ability to realize certain of its net deferred tax assets, of which $4.2 million and $24.5 million were recorded in the third and second quarter of 2014, respectively. This unfavorable impact was offset partially by $8.5 million of net tax benefit, recorded in the third quarter of 2014, associated with the release of tax reserves for uncertain tax positions as a result of the expiration of statues of limitations.
	The Company's effective rate for the nine months ended September 27, 2013 was different from the U.S. federal statutory rate of 35%, primarily attributable to the net of various discrete items, non-deductible amortization on foreign intangibles, the differential in foreign tax rates, federal research and development tax credit, and non-deductible stock-based compensation expense. The discrete items included primarily the $38.4 million tax benefit associated with the reversal of previously recorded federal and, to a lesser extent, foreign income taxes as a result of the expiration of the applicable statues of limitations in the U.S. for 2008 and 2009 and in foreign jurisdictions for various years, and the benefit associated with the reinstatement of the prior year's federal research and development tax credit, offset partially by a higher valuation allowance on California research and development tax credit and accrued interest on uncertain tax positions.
	The Company files federal, state, and foreign income tax returns in jurisdictions with varying statutes of limitations during which such tax returns may be audited and adjusted by the relevant tax authorities. The U.S. Internal Revenue Service has concluded its audit for the 2008, 2009 and 2010 tax years. The statute of limitations on the Company's 2008 and 2009 U.S. corporate income tax returns expired in September 2013, and the 2010 corporate income tax return expired in September 2014. As a result, the Company released $38.4 million of related tax reserves, including accrued interest and penalties, for the 2008 and 2009 tax years in the third quarter of 2013 and, additionally, the Company released $8.5 million of related tax reserves, including accrued interest and penalties, for the 2010 tax year in the third quarter of 2014.
	The 2011 through 2013 tax years generally remain subject to examination by U.S. federal and most state tax authorities. In significant foreign jurisdictions, the 2006 through 2013 tax years generally remain subject to examination by their respective tax authorities.
	The Company's operations in Switzerland are subject to a reduced tax rate under the Switzerland tax holiday which requires various thresholds of investment and employment in Switzerland. The Company has met these various thresholds and the Switzerland tax holiday is effective through the end of 2018.
	As of September 26, 2014, the total amount of gross unrecognized tax benefits, including interest and penalties, was approximately $16.8 million, that if recognized, would affect the Company's effective tax rate. The Company recognizes interest and penalties related to unrecognized tax positions in income tax expense. The Company had $0.3 million of gross interest and penalties accrued as of September 26, 2014. The Company will continue to review its tax positions and provide for, or reverse, unrecognized tax benefits as issues arise. As of September 26, 2014, the Company anticipates that the balance of gross unrecognized tax benefits will decrease up to approximately $0.6 million due to expiration of the applicable statues of limitations over the next twelve months.

Income_Loss_Per_Share

Income (Loss) Per Share	9 Months Ended
	Sep. 26, 2014
Earnings Per Share [Abstract]	'
Income (Loss) Per Share	'
	INCOME (LOSS) PER SHARE
	The following table sets forth the computation of the basic and diluted net income (loss) per share (in thousands, except per share amounts):
		Three months ended						Nine months ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
	Numerator:
	Income (loss) from continuing operations	$	1,078		$	36,675		$	(41,394	)	$	23,768
	Income from discontinued operations	—			91			—			15,619
	Net income (loss)	$	1,078		$	36,766		$	(41,394	)	$	39,387
	Denominator:
	Weighted average number of common shares outstanding
	Basic	90,618			101,144			94,113			108,695
	Effect of dilutive securities from stock options, restricted stock units and ESPP	1,182			1,579			—			1,184
	Diluted	91,800			102,723			94,113			109,879
	Basic net income (loss) per share from:
	Continuing operations	$	0.01		$	0.36		$	(0.44	)	$	0.22
	Discontinued operations	$	0		0			$	0		$	0.14
	Net Income (loss)	$	0.01		$	0.36		$	(0.44	)	$	0.36
	Diluted net income (loss) per share from:
	Continuing operations	$	0.01		$	0.36		$	(0.44	)	$	0.22
	Discontinued operations	$	—		$	—		$	—		$	0.14
	Net Income (loss)	$	0.01		$	0.36		$	(0.44	)	$	0.36
	The following table sets forth the potentially dilutive shares from stock options, restricted stock units and the ESPP, for the periods presented, that were excluded from the net income (loss) per share computations because their effect was anti-dilutive (in thousands):
		Three months ended					Nine months ended
		September 26,		September 27,			September 26,		September 27,
		2014		2013			2014		2013
	Potentially dilutive equity awards outstanding	5,196		6,144			9,321		10,681

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 26, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	COMMITMENTS AND CONTINGENCIES
	Leases
	Future minimum lease payments under non-cancelable operating leases as of September 26, 2014, after giving effect to $0.3 million of future sublease income from Aurora, are as follows (in thousands):
	Years ending December 31,
	2014 (remaining three months)	$	2,622
	2015	10,307
	2016	8,600
	2017	7,795
	2018	7,650
	Thereafter	13,731
	Total	$	50,705
	Warranties
	The Company accrues for estimated warranty costs at the time of product shipment. Management periodically reviews the estimated fair value of its warranty liability and records adjustments based on the terms of warranties provided to customers, historical and anticipated warranty claims experience, and estimates of the timing and cost of warranty claims. Activity for the Company’s warranty accrual, which is included in accrued liabilities, is summarized below (in thousands):
		Three months ended						Nine months ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
	Balance at beginning of period	$	3,532		$	3,228		$	3,606		$	4,292
	Transfer to Aurora as part of the sale of discontinued operations	—			—			—			(939		)
	Accrual for current period warranties	2,028			1,991			5,383			5,333
	Warranty costs incurred	(1,629		)	(1,705		)	(5,058		)	(5,172		)
	Balance at end of period	$	3,931		$	3,514		$	3,931		$	3,514
	Purchase Commitments with Contract Manufacturers and Other Suppliers
	The Company relies on a limited number of contract manufacturers and suppliers to provide manufacturing services for a substantial majority of its products. In addition, some components, sub-assemblies and modules are obtained from a sole supplier or limited group of suppliers. During the normal course of business, in order to reduce manufacturing lead times and ensure adequate component supply, the Company enters into agreements with certain contract manufacturers and suppliers that allow them to procure inventory based upon criteria defined by the Company. The Company had approximately $17.6 million of non-cancelable purchase commitments with contract manufacturers and other suppliers as of September 26, 2014.
	Standby Letters of Credit
	As of September 26, 2014, the Company’s financial guarantees consisted of standby letters of credit outstanding, which were principally related to performance bonds and state requirements imposed on employers. The maximum amount of potential future payments under these arrangements was $0.2 million as of September 26, 2014.
	Indemnification
	Harmonic is obligated to indemnify its officers and the members of its Board of Directors pursuant to its bylaws and contractual indemnity agreements. Harmonic also indemnifies some of its suppliers and most of its customers for specified intellectual property matters pursuant to certain contractual arrangements, subject to certain limitations. The scope of these indemnities varies, but, in some instances, includes indemnification for damages and expenses (including reasonable attorneys’ fees). There have been no amounts accrued in respect of these indemnification provisions through September 26, 2014.
	Guarantees
	The Company has $0.4 million of guarantees in Israel as of September 26, 2014, with the majority relating to rent obligations for buildings used by its Israeli subsidiaries.
	Legal proceedings
	From time to time, the Company is involved in lawsuits as well as subject to various legal proceedings, claims, threats of litigation, and investigations in the ordinary course of business, including claims of alleged infringement of third-party patents and other intellectual property rights, commercial, employment, and other matters. The Company assesses potential liabilities in connection with each lawsuit and threatened lawsuits and accrues an estimated loss for these loss contingencies if both of the following conditions are met: information available prior to issuance of the financial statements indicates that it is probable that a liability has been incurred at the date of the financial statements and the amount of loss can be reasonably estimated. While certain matters to which the Company is a party specify the damages claimed, such claims may not represent reasonably possible losses. Given the inherent uncertainties of litigation, the ultimate outcome of these matters cannot be predicted at this time, nor can the amount of possible loss or range of loss, if any, be reasonably estimated.
	In October 2011, Avid Technology, Inc. (“Avid”) filed a complaint in the United States District Court for the District of Delaware alleging that Harmonic’s Media Grid product infringes two patents held by Avid. A jury trial on this complaint commenced on January 23, 2014 and, on February 4, 2014, the jury returned a unanimous verdict in favor of Harmonic, rejecting Avid's infringement allegations in their entirety. Avid filed a post-trial motion asking the court to set aside the jury’s verdict.  Briefing is complete and the parties are awaiting an order on Avid’s motion.  Harmonic believes it is unlikely the judge will grant Avid’s motion.  Avid has indicated it intends to appeal the verdict if its motion is not granted.
	In June 2012, Avid served a subsequent complaint in the United States District Court for the District of Delaware alleging that Harmonic’s Spectrum product infringes one patent held by Avid. The complaint seeks injunctive relief and unspecified damages. In September 2013, the U.S. Patent Trial and Appeal Board ("PTAB") authorized an inter partes review to be instituted as to claims 1-16 of the patent asserted in this second complaint. A hearing before the PTAB was conducted on May 20, 2014. On July 10, 2014, the PTAB issued a decision finding claims 1 - 10 invalid and claims 11 - 16 not invalid. Harmonic filed an appeal with respect to the PTAB’s decision on claims 11 - 16 and the appeal has been docketed with the Federal Circuit.
	An unfavorable outcome on any litigation matter could require that Harmonic pay substantial damages, or, in connection with any intellectual property infringement claims, could require that the Company pay ongoing royalty payments or could prevent the Company from selling certain of its products. As a result, a settlement of, or an unfavorable outcome on, any of the matters referenced above or other litigation matters could have a material adverse effect on Harmonic’s business, operating results, financial position and cash flows.

Stockholders_Equity

Stockholders' Equity	9 Months Ended
	Sep. 26, 2014
Equity [Abstract]	'
Stockholders' Equity	'
	STOCKHOLDERS’ EQUITY
	Accumulated Other Comprehensive Loss
	The components of accumulated other comprehensive loss were as follows (in thousands):
		26-Sep-14			31-Dec-13
	Foreign currency translation adjustments	$	(682	)	$	(242	)
	Unrealized gain (loss) on investments	(288		)	33
	Accumulated other comprehensive loss	$	(970	)	$	(209	)
	Common Stock Repurchases
	On April 24, 2012, our Board of Directors (the "Board") approved a stock repurchase program that provided for the repurchase of up to $25 million of our outstanding common stock. During 2013, the Board approved $195 million of increases to the program, increasing the aggregate authorized amount of the program to $220 million. On February 6, 2013, the Board approved a modification to the program that permits the Company to also repurchase its common stock pursuant to a plan that meets the requirements of Rule 10b5-1 under the Securities Exchange Act of 1934. On May 14, 2014, the Board approved an increase to the aggregate amount authorized under the repurchase program of $80 million and extended the repurchase period through the end of 2016.
	As of September 26, 2014, we had purchased 36.3 million shares of common stock under this program at a weighted average price of $6.19 per share for an aggregate purchase price of $224.6 million, excluding fees. The remaining authorized amount for stock repurchases under this program was $75.4 million as of September 26, 2014. For additional information, see "Item2 - Unregistered sales of equity securities and use of proceeds" of this Form 10-Q.

Subsequent_Event

Subsequent Event	9 Months Ended
	Sep. 26, 2014
Subsequent Event [Line Items]	'
Subsequent Events	'
	SUBSEQUENT EVENT
	On October 22, 2014, the Company acquired an approximately 18.4% ownership interest on a fully diluted basis in Encoding.com, Inc., a San Francisco-based provider of cloud-based transcoding and other media processing services, through an investment in Encoding.com's Series B financing round.

Basis_of_Presentation_and_Sign1

Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 26, 2014
Accounting Policies [Abstract]	'
Discontinued Operations	'
	Discontinued Operations
	In the first quarter of fiscal 2013, the Company completed the sale of its cable access hybrid-fiber coaxial ("HFC") business to Aurora Networks (“Aurora”). The results of operations associated with the cable access HFC business were presented as discontinued operations in its unaudited condensed consolidated financial statements as described in Note 3, "Discontinued Operations". There were no operating activities associated with the cable access HFC business after December 31, 2013. Unless noted otherwise, all discussions herein with respect to the Company’s unaudited condensed consolidated financial statements relate to the Company’s continuing operations.
Use of Estimates	'
	Use of Estimates
	The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates.
Variable Interest Entities	'
	Variable Interest Entities
	From time to time, the Company may enter into investments in entities that are considered variable interest entities under Accounting Standards Codification (ASC) Topic 810. If the Company is the primary beneficiary of a variable interest entity ("VIE"), it is required to consolidate it. To determine if the Company is the primary beneficiary of a VIE, the Company evaluates whether it has (1) the power to direct the activities that most significantly impact the VIE's economic performance, and (2) the obligation to absorb losses or the right to receive benefits from the VIE that could potentially be significant to the VIE. The assessment of whether the Company is the primary beneficiary of its VIE requires significant assumptions and judgments.
Investment in Equity Securities	'
	Investments in Equity Securities
	The Company accounts for its investments in entities that it does not have significant influence under the cost method. Investments in equity securities are carried at fair value if the fair value of the security is readily determinable. Equity investments carried at fair value are classified as long-term investments and included in "Other assets" in the Company's Condensed Consolidated Balance Sheet. Unrealized gains and losses, net of taxes, on the long-term investments are included in the Company's Condensed Consolidated Balance Sheet as a component of accumulated other comprehensive income (loss). Investments in equity securities that do not qualify for fair value accounting or equity method accounting are accounted for under the cost method. In accordance with the cost method, the Company's initial investment is recorded at cost and the Company reviews all of its cost method investments quarterly to determine if impairment indicators exist. Cost method investments are classified as long-term investments and included in "Other assets" in the Company's Condensed Consolidated Balance Sheet.
Segment Reporting	'
	Segment Reporting
	The Company operates its business in one reportable segment, which is the design, manufacture and sale of versatile and high performance video infrastructure products and system solutions. Operating segments are defined as components of an enterprise that engage in business activities for which separate financial information is available and evaluated by the chief operating decision  maker (which for Harmonic is the Chief Executive Officer) in deciding how to allocate resources and assess performance. More recently, the Company has started to view its business through two market segments: Video and Cable Edge. As part of its annual year-end financial planning process, the Company expects to develop internal processes, policies and controls to enable timely and reliable measuring of operating profits by these segments. The Company expects the chief operating decision maker will apply this information in deciding how to allocate resources and assess the Company's performance. As such, the Company anticipates reporting the operating results for the Video and Cable Edge business in its segment reporting in the fourth quarter of 2014.
Significant Accounting Policies	'
	Significant Accounting Policies
	The Company’s significant accounting policies are described in Note 2 to its audited Consolidated Financial Statements included in its 2013 Form 10-K. There have been no significant changes to these policies during the nine months ended September 26, 2014.
Recent Accounting Pronouncements	'
	RECENT ACCOUNTING PRONOUNCEMENTS
	In March 2013, the FASB issued ASU 2013-05, “Parent’s Accounting for the Cumulative Translation Adjustment upon De-recognition of Certain Subsidiaries or Groups of Assets within a Foreign Entity or of an Investment in a Foreign Entity”. The ASU addresses accounting for a cumulative translation adjustment when a parent either sells a part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or group of assets that is a nonprofit activity or a business within a foreign entity. The new guidance became effective for the Company beginning in the first quarter of fiscal 2014 and it did not have a material impact on the Company’s Consolidated Financial Statements.
	In July 2013, the FASB issued ASU 2013-11, “Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists”. Under certain circumstances, unrecognized tax benefits should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward. The new guidance became effective for the Company beginning in the first quarter of fiscal 2014 and it did not have a material impact on the Company’s Consolidated Financial Statements.
	On April 10, 2014, the FASB issued ASU 2014-08, “Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity". This guidance raises the threshold for a disposal to qualify as a discontinued operation and requires new disclosures of both discontinued operations and certain other disposals that do not meet the definition of a discontinued operation. The guidance is effective for the Company beginning in the first quarter of fiscal 2015. The Company does not expect the adoption of ASU 2014-08 will have a material impact on its financial position, results of operations or cash flows.
	On May 28, 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers", requiring an entity to recognize the amount of revenue that reflects the consideration to which it expects to be entitled for the transfer of promised goods or services to customers. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective and permits the use of either the retrospective or cumulative effect transition method. Early adoption is not permitted. The updated standard becomes effective for the Company in the first quarter of fiscal 2017. We have not yet selected a transition method and we are currently evaluating the effect that the updated standard will have on our consolidated financial statements and related disclosures.
Impairment of Investments	'
	Impairment of Investments
	The Company monitors its investment portfolio for impairment on a periodic basis. In the event that the carrying value of an investment exceeds its fair value and the decline in value is determined to be other-than-temporary, an impairment charge is recorded and a new cost basis for the investment is established. A decline of fair value below amortized costs of debt securities is considered other-than-temporary if the Company has the intent to sell the security or it is more likely than not that the Company will be required to sell the security before recovery of the entire amortized cost basis. At the present time, the Company does not intend to sell its investments that have unrealized losses in accumulated other comprehensive loss. In addition, the Company does not believe that it is more likely than not that it will be required to sell its investments that have unrealized losses in accumulated other comprehensive loss before the Company recovers the principal amounts invested. The Company believes that the unrealized losses are temporary and do not require an other-than-temporary impairment, based on its evaluation of available evidence as of September 26, 2014.
	As of September 26, 2014, there were no individual available-for-sale securities in a material unrealized loss position and the amount of unrealized losses on the total investment balance was insignificant.
Derivatives and Hedging Activities	'
	The Company enters into foreign currency forward contracts to minimize the short-term impact of foreign currency exchange rate fluctuations on cash and certain trade and inter-company receivables and payables, primarily denominated in Euro, British pound, Japanese yen and Israeli shekel. These contracts reduce the exposure to fluctuations in foreign currency exchange rate movements as the gains and losses associated with foreign currency balances are generally offset with the gains and losses on the forward contracts. These contracts are not designated as hedges that are eligible for hedge accounting treatment and are marked to market through earnings every period and generally range from one to three months in original maturity. The Company does not enter into foreign currency forward contacts for trading purposes.
Fair Value of Financial Instruments	'
	The applicable accounting guidance establishes a framework for measuring fair value and requires disclosure about the fair value measurements of assets and liabilities. This guidance requires the Company to classify and disclose assets and liabilities measured at fair value on a recurring basis, as well as fair value measurements of assets and liabilities measured on a nonrecurring basis in periods subsequent to initial measurement, in a three-tier fair value hierarchy as described below.
	The guidance defines fair value as the exchange price that would be received for an asset or paid to transfer a liability, in the principal or most advantageous market for the asset or liability, in an orderly transaction between market participants on the measurement date.
	Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The guidance describes three levels of inputs that may be used to measure fair value:
	•	Level 1 — Observable inputs that reflect quoted prices for identical assets or liabilities in active markets.
	•	Level 2 — Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. The Company primarily uses broker quotes for valuation of its short-term investments. The forward exchange contracts are classified as Level 2 because they are valued using quoted market prices and other observable data for similar instruments in an active market.
	•	Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
	The Company uses the market approach to measure fair value for its financial assets and liabilities. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities. During the nine months ended September 26, 2014, there were no nonrecurring fair value measurements of assets and liabilities subsequent to initial recognition.
Share-based Compensation Expense	'
	Stock Options
	The Company estimated the fair value of all employee stock options using a Black-Scholes valuation model with the following weighted average assumptions:
		Three months ended				Nine months ended
		September 26,		September 27,		September 26,		September 27,
		2014		2013		2014		2013
	Expected term (years)	4.7		4.7		4.7		4.7
	Volatility	40	%	46	%	40	%	51	%
	Risk-free interest rate	1.8	%	1.5	%	1.7	%	0.8	%
	Expected dividends	0	%	0	%	0	%	0	%
	The expected term represents the weighted-average period that the stock options are expected to remain outstanding. The computation of the expected term was determined based on historical experience of similar awards, giving consideration to the contractual terms of the stock-based awards, vesting schedules and expectations of future employee behavior. The Company uses its historical volatility for a period equivalent to the expected term of the options to estimate the expected volatility. The risk-free interest rate that the Company uses in the Black-Scholes option valuation model is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected term. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future, and, therefore, used an expected dividend yield of zero in the valuation model.
	The Company is required to estimate forfeitures at the time of grant and revise those estimates in subsequent periods if actual forfeitures differ from those estimates. The Company uses historical data to estimate pre-vesting option forfeitures and records stock-based compensation expense only for those awards that are expected to vest. All stock-based payment awards are amortized on a straight-line basis over the requisite service periods of the awards, which are generally the vesting periods.
	The weighted-average fair value per share of options granted was $2.48 and $3.02 for the three months ended September 26, 2014 and September 27, 2013, respectively. The weighted-average fair value per share of options granted was $2.36 and $2.51 for the nine months ended September 26, 2014 and September 27, 2013, respectively.
	The fair value of all stock options vested during the three months ended September 26, 2014 and September 27, 2013 was $0.6 million and $0.8 million respectively. The fair value of all stock options vested during the nine months ended September 26, 2014 and September 27, 2013 was $2.6 million and $2.8 million respectively.
	The total realized tax benefit attributable to stock options exercised during the nine months ended September 26, 2014, in jurisdictions where this expense is deductible for tax purposes, was $194,000. The Company did not recognize any tax benefit attributable to stock options exercised during the nine months ended September 27, 2013.
	Restricted Stock Units
	The aggregate fair value of all restricted stock units issued during the three months ended September 26, 2014 and September 27, 2013 was $2.7 million and $2.8 million respectively. The estimated fair value of all restricted stock units issued during the nine months ended September 26, 2014 and September 27, 2013 were $10.0 million and $10.2 million respectively.
	Employee Stock Purchase Plan
	The value of the stock purchase rights under the ESPP consists of: (1) the 15% discount on the purchase of the stock; (2) 85% of the fair value of the call option; and (3) 15% of the fair value of the put option. The call option and put option were valued using the Black-Scholes option pricing model. The weighted average fair value of the Company's ESPP shares at purchase dates was estimated using the following weighted average assumptions during the nine months ended September 26, 2014 and September 27, 2013:
		Purchase Period Ending
		December 31,		June 30,		June 30,
		2014		2014		2013
	Expected term (years)	0.5		0.5		0.49
	Volatility	33	%	28	%	30	%
	Risk-free interest rate	0.1	%	0.1	%	0.2	%
	Expected dividends	0	%	0	%	0	%
	Estimated weighted average fair value per share at purchase date	$1.84		$1.70		$1.23
	The expected term represents the period of time from the beginning of the offering period to the purchase date. The Company uses its historical volatility for a period equivalent to the expected term of the options to estimate the expected volatility. The risk-free interest rate that the Company uses in the Black-Scholes option valuation model is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected term. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future, and, therefore, used an expected dividend yield of zero in the valuation model.
	The ESPP was suspended for the second half of 2013 due to all authorized shares under the plan having been issued through the offering period ended June 30, 2013. The Company’s stockholders approved a 1,000,000 share increase in the authorized shares for the ESPP during the Company’s annual meeting on August 14, 2013, and contributions under the ESPP resumed in January 2014. As a result, the Company did not have any stock-based compensation expense in the second half of fiscal 2013 related to the ESPP.
	Unrecognized Stock-Based Compensation
	As of September 26, 2014, total unamortized stock-based compensation cost related to unvested stock options and restricted stock units was $17.1 million. This amount will be recognized as expense using the straight-line attribution method over the remaining weighted-average vesting period of 1.7 years.
Income Tax	'
	As of September 26, 2014, the total amount of gross unrecognized tax benefits, including interest and penalties, was approximately $16.8 million, that if recognized, would affect the Company's effective tax rate. The Company recognizes interest and penalties related to unrecognized tax positions in income tax expense. The Company had $0.3 million of gross interest and penalties accrued as of September 26, 2014. The Company will continue to review its tax positions and provide for, or reverse, unrecognized tax benefits as issues arise. As of September 26, 2014, the Company anticipates that the balance of gross unrecognized tax benefits will decrease up to approximately $0.6 million due to expiration of the applicable statues of limitations over the next twelve months.
Warranties and Indemnification	'
	The Company accrues for estimated warranty costs at the time of product shipment. Management periodically reviews the estimated fair value of its warranty liability and records adjustments based on the terms of warranties provided to customers, historical and anticipated warranty claims experience, and estimates of the timing and cost of warranty claims.
	Harmonic is obligated to indemnify its officers and the members of its Board of Directors pursuant to its bylaws and contractual indemnity agreements. Harmonic also indemnifies some of its suppliers and most of its customers for specified intellectual property matters pursuant to certain contractual arrangements, subject to certain limitations. The scope of these indemnities varies, but, in some instances, includes indemnification for damages and expenses (including reasonable attorneys’ fees).

Discontinued_Operations_Tables

Discontinued Operations (Tables)	9 Months Ended
	Sep. 26, 2014
Discontinued Operations and Disposal Groups [Abstract]	'
Schedule of Discontinued Operations, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures	'
	Revenue and the components of net income related to the discontinued operations for the three and nine months ended September 27, 2013 were as follows (in thousands):
		Three months ended			Nine months ended
		27-Sep-13
	Revenue	$	161		$	9,717
	Operating income	$	154		$	669
	Less : Provision for (benefit from) income taxes	57			(137		)
	Add : Gain (loss) on disposal, net of taxes	(6		)	14,813
	Income from discontinued operations, net of taxes	$	91		$	15,619
	The table below provides details on the income statement caption under which the TSA billing was recorded (in thousands):
		Three months ended			Nine months ended
		27-Sep-13
	Product cost of revenue	$	41		$	577
	Research and development	—			21
	Selling, general and administrative	7			379
	Total TSA billing to Aurora	$	48		$	977
	The Company recorded a gain of $14.8 million in the nine months ended September 27, 2013 , in connection with the sale of the cable access HFC business, calculated as follows (in thousands):
	Gross Proceeds				$	46,000
	Less : Carrying value of net assets
	Inventories, net	$	10,579
	Prepaid expenses and other current assets	612
	Property and equipment, net	1,180
	Goodwill de-recognized	14,547
	Deferred revenue	(4,499		)
	Accrued liabilities	(939		)
	Total net assets sold and de-recognized				$	21,480
	Less : Selling cost				2,473
	Less : Tax effect				7,234
	Gain on disposal, net of taxes				$	14,813

ShortTerm_Investments_Tables

Short-Term Investments (Tables)	9 Months Ended
	Sep. 26, 2014
Cash and Cash Equivalents [Abstract]	'
Summary of Short-Term Investments	'
	The following table summarizes the Company’s short-term investments (in thousands):
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	As of September 26, 2014
	State, municipal and local government agencies bonds	$	25,719	$	26	$	(31	)	$	25,714
	Corporate bonds	26,150		5		(17		)	26,138
	Commercial paper	3,299		—		—			3,299
	U.S. federal government bonds	—		—		—			—
	Total short-term investments	$	55,168	$	31	$	(48	)	$	55,151
	As of December 31, 2013
	State, municipal and local government agencies bonds	$	40,426	$	38	$	(15	)	$	40,449
	Corporate bonds	33,483		20		(7		)	33,496
	Commercial paper	2,299		—		—			2,299
	U.S. federal government bonds	4,004		4		—			4,008
	Total short-term investments	$	80,212	$	62	$	(22	)	$	80,252
Maturities of Short-Term Investments	'
	The following table summarizes the maturities of the Company’s short-term investments (in thousands):
		26-Sep-14		31-Dec-13
	Less than one year	$	44,452	$	55,278
	Due in 1 - 2 years	10,699		24,974
	Total short-term investments	$	55,151	$	80,252

Derivative_and_Hedging_Activit

Derivative and Hedging Activities (Tables)	9 Months Ended
	Sep. 26, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivatives Not Designated as Hedging Instruments, Balance Sheet Location	'
	The balance sheet location and net fair value of each of the Company’s derivatives are as follows (in thousands):
				Fair Value of Asset (Liability)
	Derivatives not designated as hedging instruments	Balance Sheet Location		26-Sep-14				31-Dec-13
	Foreign currency contracts	Prepaid expenses and other current assets		$	19			$	196
	Foreign currency contracts	Accrued liabilities		(331		)		(195		)
Changes in fair values of non-designated foreign currency forward contracts	'
	The effects of the changes in the fair values of non-designated foreign currency forward contracts are summarized as follows (in thousands) :
		Three Months Ended								Nine months ended
		26-Sep-14				27-Sep-13				26-Sep-14			27-Sep-13
	Gain (loss) recorded in other income (expense), net	$	(95	)		$	(157	)		$	(201	)	$	658

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 26, 2014
Fair Value Disclosures [Abstract]	'
Financial Assets and Liabilities Measured at Fair Value Based on Three-Tier Fair Value Hierarchy	'
	The following table sets forth the fair value of the Company’s financial assets and liabilities measured at fair value based on the three-tier fair value hierarchy (in thousands):
		Level 1		Level 2		Level 3		Total
	As of September 26, 2014
	Cash equivalents
	Money market funds	$	4,292	$	—	$	—	$	4,292
	Short-term investments
	State, municipal and local government agencies bonds	—		25,714		—		25,714
	Corporate bonds	—		26,138		—		26,138
	Commercial paper	—		3,299		—		3,299
	U.S. federal government bonds			—		—		—
	Prepaids and other current assets
	Derivative assets (1)	—		19		—		19
	Other assets
	Long-term investment	3,101						3,101
	Total assets measured and recorded at fair value	$	7,393	$	55,170	$	—	$	62,563
	Accrued liabilities
	Derivative liabilities (1)	$	—	$	331	$	—	$	331
	Total liabilities measured and recorded at fair value	$	—	$	331	$	—	$	331
		Level 1		Level 2		Level 3		Total
	As of December 31, 2013
	Cash equivalents
	Money market funds	$	51,014	$	—	$	—	$	51,014
	Short-term investments
	State, municipal and local government agencies bonds	—		40,449		—		40,449
	Corporate bonds	—		33,496		—		33,496
	Commercial paper	—		2,299		—		2,299
	U.S. federal government bonds	4,008		—		—		4,008
	Prepaids and other current assets
	Derivative assets (1)	—		196		—		196
	Total assets measured and recorded at fair value	$	55,022	$	76,440	$	—	$	131,462
	Accrued liabilities
	Derivative liabilities (1)	$	—	$	195	$	—	$	195
	Total liabilities measured and recorded at fair value	$	—	$	195	$	—	$	195

Balance_Sheet_Components_Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 26, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Accounts Receivable, Net	'
		26-Sep-14			31-Dec-13
	Accounts receivable, net:
	Accounts receivable	$	81,988		$	83,266
	Less: allowances for doubtful accounts, returns and discounts	(6,348		)	(8,214		)
	Accounts receivable, net	$	75,640		$	75,052
Inventories	'
	Inventories:
	Raw materials	$	1,805		$	2,389
	Work-in-process	1,780			976
	Finished goods	28,927			33,561
		$	32,512		$	36,926
Property and Equipment, Net	'
	Property and equipment, net:
	Furniture and fixtures	$	8,796		$	8,227
	Machinery and equipment	117,765			114,178
	Leasehold improvements	8,386			7,888
	Property and equipment, gross	134,947			130,293
	Less: accumulated depreciation and amortization	(104,133		)	(95,348		)
		$	30,814		$	34,945

Goodwill_and_Identified_Intang1

Goodwill and Identified Intangible Assets (Tables)	9 Months Ended
	Sep. 26, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Changes in Carrying Amount of Goodwill	'
	The changes in the carrying amount of goodwill for the nine months ended September 26, 2014 are as follows (in thousands):
	Balance at beginning of period	$	198,022
	Foreign currency translation adjustment	(15		)
	Balance at end of period	$	198,007
Summary of Goodwill and Identified Intangible Assets	'
	The following is a summary of identified intangible assets (in thousands):
				26-Sep-14												31-Dec-13
		Range of Useful Lives		Gross Carrying				Accumulated				Net Carrying				Gross Carrying		Accumulated			Net Carrying
				Amount				Amortization				Amount				Amount		Amortization			Amount
	Identifiable intangibles:
	Developed core technology	4-6 years		$	136,145			$	(134,731	)		$	1,414			$	136,145	$	(121,681	)	$	14,464
	Customer relationships/contracts	5-6 years		67,098				(57,568		)		9,530				67,098		(53,772		)	13,326
	Trademarks and tradenames	4-5 years		11,361				(11,361		)		—				11,361		(10,565		)	796
	Maintenance agreements and related relationships	6-7 years		7,100				(5,304		)		1,796				7,100		(4,567		)	2,533
	Total identifiable intangibles			$	221,704			$	(208,964	)		$	12,740			$	221,704	$	(190,585	)	$	31,119
Amortization Expense for Identifiable Purchased Intangible Assets	'
	Amortization expense for the identifiable purchased intangible assets for the three and nine months ended September 26, 2014 and September 27, 2013 was allocated as follows (in thousands):
		Three months ended								Nine months ended
		September 26,				September 27,				September 26,				September 27,
		2014				2013				2014				2013
	Included in cost of revenue	$	3,851			$	4,763			$	13,049			$	14,470
	Included in operating expenses	1,661				2,001				5,329				6,099
	Total amortization expense	$	5,512			$	6,764			$	18,378			$	20,569
Estimated Future Amortization Expense of Purchased Intangible Assets	'
	The estimated future amortization expense of purchased intangible assets with definite lives is as follows (in thousands):
		Cost of Revenue				Operating				Total
						Expenses
	Year ended December 31,
	2014 (remaining 3 months)	$	695			$	1,446			$	2,141
	2015	719				5,783				6,502
	2016	—				4,097				4,097
	Total future amortization expense	$	1,414			$	11,326			$	12,740

Restructuring_and_Related_Char1

Restructuring and Related Charges (Tables)	9 Months Ended
	Sep. 26, 2014
Restructuring Cost and Reserve [Line Items]	'
Summary of restructuring activities	'
	The following table summarizes the restructuring and related charges (in thousands):
		Three months ended					Nine months ended
		September 26,			September 27,		September 26,			September 27,
		2014			2013		2014			2013
	Restructuring and related charges in:
	Product cost of revenue	$	15		$	324	$	94		$	530
	Operating expenses-Restructuring and related charges	388			259		821			925
		$	403		$	583	$	915		$	1,455
Harmonic Two Thousand And Thirteen Restructuring [Member]	'
Restructuring Cost and Reserve [Line Items]	'
Schedule of Restructuring Reserve by Type of Cost [Table Text Block]	'
	The following table summarizes the activity in the restructuring accrual under this plan during the nine months ended September 26, 2014 (in thousands):
		Severance			Termination of a research & development project		Excess facilities			Total
	Balance at December 31, 2013	$	179		$	—	$	—		$	179
	2013 Plan restructuring charges	829			63		32			924
	Adjustments to restructuring provisions	(9		)	—		—			(9		)
	Cash payments	(715		)	—		(32		)	(747		)
	Balance at September 26, 2014	$	284		63		$	—		$	347

Employee_Benefit_Plans_Tables

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 26, 2014
Postemployment Benefits [Abstract]	'
Summary of Company's Stock Option and Restricted Stock Unit Activity	'
	The following table summarizes the Company’s stock option and RSU unit activity during the nine months ended September 26, 2014 (in thousands, except per share amounts):
				Stock Options Outstanding						Restricted Stock Units Outstanding
		Shares		Number			Weighted			Number		Weighted
		Available for		of			Average			of		Average
		Grant		Shares			Exercise Price			Units		Grant
												Date Fair
												Value
	Balance at December 31, 2013	8,752		7,885			$	6.92		3,018		$	6.34
	Authorized	350		—			—			—		—
	Granted	(3,477	)	1,450			6.52			1,352		6.55
	Options exercised	—		(329	)		4.91			—		—
	Shares released	—		—			—			(1,589	)	6.32
	Forfeited or cancelled	1,753		(1,592	)		8.15			(232	)	6.13
	Balance at September 26, 2014	7,378		7,414			$	6.67		2,549		$	6.49
Summary of Stock Options Outstanding	'
	The following table summarizes information about stock options outstanding as of September 26, 2014 (in thousands, except per share amounts):
		Number		Weighted				Weighted	Aggregate
		of		Average				Average	Intrinsic
		Shares		Exercise				Remaining	Value
				Price				Contractual
								Term (Years)
	Vested and expected to vest	7,095		$	6.68			3.6	$	3,118
	Exercisable	4,760		6.84				2.5	2,519
Summary of Restricted Stock Units Outstanding	'
	The following table summarizes information about restricted stock units outstanding as of September 26, 2014 (in thousands, except per share amounts):
		Number of		Weighted		Aggregate
		Shares		Average		Fair
		Underlying		Remaining		Value
		Restricted		Vesting
		Stock		Period
		Units		(Years)
	Vested and expected to vest	2,365		0.7		$	15,114

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 26, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Summary of Stock-Based Compensation Expense	'
	The following table summarizes stock-based compensation expense (in thousands):
		Three months ended							Nine months ended
		September 26,			September 27,				September 26,			September 27,
		2014			2013				2014			2013
	Stock-based compensation in:
	Cost of revenue	$	612		$	605			$	1,751		$	1,838
	Research and development expense	1,219			1,076				3,589			3,400
	Selling, general and administrative expense	2,521			2,264				7,380			6,628
	Total stock-based compensation in operating expense	3,740			3,340				10,969			10,028
	Total stock-based compensation	$	4,352		$	3,945			$	12,720		$	11,866
Valuation Assumptions for Stock Options	'
	The Company estimated the fair value of all employee stock options using a Black-Scholes valuation model with the following weighted average assumptions:
		Three months ended					Nine months ended
		September 26,		September 27,			September 26,			September 27,
		2014		2013			2014			2013
	Expected term (years)	4.7		4.7			4.7			4.7
	Volatility	40	%	46	%		40	%		51	%
	Risk-free interest rate	1.8	%	1.5	%		1.7	%		0.8	%
	Expected dividends	0	%	0	%		0	%		0	%
Employee Stock Purchase Plan	'
	The call option and put option were valued using the Black-Scholes option pricing model. The weighted average fair value of the Company's ESPP shares at purchase dates was estimated using the following weighted average assumptions during the nine months ended September 26, 2014 and September 27, 2013:
		Purchase Period Ending
		December 31,		June 30,			June 30,
		2014		2014			2013
	Expected term (years)	0.5		0.5			0.49
	Volatility	33	%	28	%		30	%
	Risk-free interest rate	0.1	%	0.1	%		0.2	%
	Expected dividends	0	%	0	%		0	%
	Estimated weighted average fair value per share at purchase date	$1.84		$1.70			$1.23

Income_Taxes_Tables

Income Taxes (Tables)	9 Months Ended
	Sep. 26, 2014
Income Tax Disclosure [Abstract]	'
Schedule of income before income tax	'
	The Company reported the following operating results for the periods presented (in thousands):
		Three months ended						Nine months ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
	Loss from continuing operations before income taxes	$	(3,752	)	$	(2,278	)	$	(19,594	)	$	(21,955	)
	Provision for (benefit from) income taxes	(4,830		)	(38,953		)	21,800			(45,723		)
	Effective income tax rate	128.7		%	1,710.00		%	(111.3		)%	208.3		%

Income_Loss_Per_Share_Tables

Income (Loss) Per Share (Tables)	9 Months Ended
	Sep. 26, 2014
Earnings Per Share [Abstract]	'
Numerators and Denominators of Basic and Diluted Net Income (Loss) Per Share Computations	'
	The following table sets forth the computation of the basic and diluted net income (loss) per share (in thousands, except per share amounts):
		Three months ended						Nine months ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
	Numerator:
	Income (loss) from continuing operations	$	1,078		$	36,675		$	(41,394	)	$	23,768
	Income from discontinued operations	—			91			—			15,619
	Net income (loss)	$	1,078		$	36,766		$	(41,394	)	$	39,387
	Denominator:
	Weighted average number of common shares outstanding
	Basic	90,618			101,144			94,113			108,695
	Effect of dilutive securities from stock options, restricted stock units and ESPP	1,182			1,579			—			1,184
	Diluted	91,800			102,723			94,113			109,879
	Basic net income (loss) per share from:
	Continuing operations	$	0.01		$	0.36		$	(0.44	)	$	0.22
	Discontinued operations	$	0		0			$	0		$	0.14
	Net Income (loss)	$	0.01		$	0.36		$	(0.44	)	$	0.36
	Diluted net income (loss) per share from:
	Continuing operations	$	0.01		$	0.36		$	(0.44	)	$	0.22
	Discontinued operations	$	—		$	—		$	—		$	0.14
	Net Income (loss)	$	0.01		$	0.36		$	(0.44	)	$	0.36
Anti-dilutive Securities	'
	The following table sets forth the potentially dilutive shares from stock options, restricted stock units and the ESPP, for the periods presented, that were excluded from the net income (loss) per share computations because their effect was anti-dilutive (in thousands):
		Three months ended					Nine months ended
		September 26,		September 27,			September 26,		September 27,
		2014		2013			2014		2013
	Potentially dilutive equity awards outstanding	5,196		6,144			9,321		10,681

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 26, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Future Minimum Lease Payments Under Non-cancelable Operating Leases	'
	Future minimum lease payments under non-cancelable operating leases as of September 26, 2014, after giving effect to $0.3 million of future sublease income from Aurora, are as follows (in thousands):
	Years ending December 31,
	2014 (remaining three months)	$	2,622
	2015	10,307
	2016	8,600
	2017	7,795
	2018	7,650
	Thereafter	13,731
	Total	$	50,705
Summary of Warranty Accrual Included in Accrued Liabilities	'
	Activity for the Company’s warranty accrual, which is included in accrued liabilities, is summarized below (in thousands):
		Three months ended						Nine months ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
	Balance at beginning of period	$	3,532		$	3,228		$	3,606		$	4,292
	Transfer to Aurora as part of the sale of discontinued operations	—			—			—			(939		)
	Accrual for current period warranties	2,028			1,991			5,383			5,333
	Warranty costs incurred	(1,629		)	(1,705		)	(5,058		)	(5,172		)
	Balance at end of period	$	3,931		$	3,514		$	3,931		$	3,514

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 26, 2014
Equity [Abstract]	'
Components of Accumulated Other Comprehensive Loss	'
	The components of accumulated other comprehensive loss were as follows (in thousands):
		26-Sep-14			31-Dec-13
	Foreign currency translation adjustments	$	(682	)	$	(242	)
	Unrealized gain (loss) on investments	(288		)	33
	Accumulated other comprehensive loss	$	(970	)	$	(209	)

Basis_of_Presentation_and_Sign2

Basis of Presentation and Significant Accounting Policies Summary of Presentation and Significant Accounting Policies (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013	Dec. 31, 2014	Sep. 26, 2014
		segment	segment		Scenario, Forecast [Member]	Cable Access Business [Member]
					segment
Summary Of Significant Accounting Policies [Line Items]	'	'	'	'	'	'
Operating Income (Loss)	($3,538,000)	($2,555,000)	($19,409,000)	($22,026,000)	'	$0
Number of Reportable Segments	'	1	1	'	2	'

Discontinued_Operations_Additi

Discontinued Operations - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		1 Months Ended	3 Months Ended	9 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013	Sep. 27, 2013	Mar. 29, 2013	Sep. 26, 2014	Sep. 27, 2013	Mar. 05, 2013	Sep. 27, 2013	Sep. 27, 2013
		segment	segment		HFC business [Member]	HFC business [Member]	HFC business [Member]	HFC business [Member]	Aurora [Member]	Aurora [Member]	Aurora [Member]
									HFC business [Member]	HFC business [Member]	HFC business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Gross proceeds from sale of cable access HFC business	'	'	'	'	'	'	'	$46,000,000	$46,000,000	'	'
Gain on disposal, net of taxes	'	'	0	14,813,000	-6,000	'	'	14,813,000	'	14,800,000	15,000,000
Adjustment to prior period gain (loss) on disposal, net of tax	'	'	'	'	'	'	'	'	'	'	-200,000
Number of reporting units (in segment)	'	1	1	'	'	'	'	'	'	'	'
Carrying value of goodwill based on the fair value	'	'	'	'	14,547,000	'	'	14,547,000	'	'	'
Goodwill impairment	'	'	'	'	'	0	'	'	'	'	'
Operating Income (Loss)	($3,538,000)	($2,555,000)	($19,409,000)	($22,026,000)	'	'	$0	'	'	'	'

Discontinued_Operations_Schedu

Discontinued Operations - Schedule of Details on Income Statement Caption on TSA Billing (Detail) (Aurora [Member], USD $)	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'
Total TSA billing to Aurora	$48	$977
Product cost of revenue [Member]	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'
Total TSA billing to Aurora	41	577
Research and development expense [Member]	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'
Total TSA billing to Aurora	0	21
Selling, general and administrative expenses [Member]	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'
Total TSA billing to Aurora	$7	$379

Discontinued_Operations_Record

Discontinued Operations - Recorded Gain With the Sale of Cable Access HFC Business (Detail) (USD $)	9 Months Ended		3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 27, 2013	Sep. 27, 2013
			HFC business [Member]	HFC business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Gross Proceeds	'	'	'	$46,000
Inventories, net	'	'	10,579	10,579
Prepaid expenses and other current assets	'	'	612	612
Property and equipment, net	'	'	1,180	1,180
Goodwill de-recognized	'	'	14,547	14,547
Deferred revenue	'	'	-4,499	-4,499
Accrued liabilities	'	'	-939	-939
Total net assets sold and de-recognized	'	'	21,480	21,480
Less : Selling cost	'	'	'	2,473
Less : Tax effect	'	'	'	7,234
Gain on disposal, net of taxes	$0	$14,813	($6)	$14,813

Discontinued_Operations_Revenu

Discontinued Operations - Revenues and Components of Net Income Related to Discontinued Operations (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Add : Gain (loss) on disposal, net of taxes	'	'	$0	$14,813
Income from discontinued operations, net of taxes	0	91	0	15,619
HFC business [Member]	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Revenue	'	161	'	9,717
Operating income	'	154	'	669
Less : Provision for (benefit from) income taxes	'	57	'	-137
Add : Gain (loss) on disposal, net of taxes	'	-6	'	14,813
Income from discontinued operations, net of taxes	'	$91	'	$15,619

Investments_in_Equity_Securiti1

Investments in Equity Securities (Details) (USD $)	Sep. 26, 2014	Dec. 31, 2013	Sep. 26, 2014	Sep. 02, 2014	Sep. 26, 2014	Sep. 26, 2014
			VJU GmbH [Member]	Vislink plc [Member]	Cost-method Investments [Member]	Research and development expense [Member]
					Variable Interest Entity, Not Primary Beneficiary [Member]	Variable Interest Entity, Not Primary Beneficiary [Member]
					VJU GmbH [Member]	VJU GmbH [Member]
Schedule of Cost-method Investments [Line Items]	'	'	'	'	'	'
Noncontrolling Interest, Ownership Percentage by Parent	'	'	19.80%	3.30%	'	'
Cost Method Investments Original Cost	'	'	$2,500,000	$3,300,000	'	'
Prepaid expenses and other current assets	26,852,000	21,521,000	'	3,300,000	'	'
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	'	'	'	'	2,500,000	100,000
Cost Method Investments Carrying Value	'	'	'	$3,100,000	'	'

ShortTerm_Investments_Summary_

Short-Term Investments - Summary of Short-Term Investments (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	$55,168	$80,212
Gross Unrealized Gains	31	62
Gross Unrealized Losses	-48	-22
Total short-term investments, Estimated Fair Value	55,151	80,252
State, municipal and local government agencies bonds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	25,719	40,426
Gross Unrealized Gains	26	38
Gross Unrealized Losses	-31	-15
Total short-term investments, Estimated Fair Value	25,714	40,449
Corporate bonds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	26,150	33,483
Gross Unrealized Gains	5	20
Gross Unrealized Losses	-17	-7
Total short-term investments, Estimated Fair Value	26,138	33,496
Commercial paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	3,299	2,299
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Total short-term investments, Estimated Fair Value	3,299	2,299
U.S. federal government bonds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	0	4,004
Gross Unrealized Gains	0	4
Gross Unrealized Losses	0	0
Total short-term investments, Estimated Fair Value	$0	$4,008

ShortTerm_Investments_Maturiti

Short-Term Investments - Maturities of Short-Term Investments (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Investments, Debt and Equity Securities [Abstract]	'	'
Less than one year	$44,452	$55,278
Due in 1 - 2 years	10,699	24,974
Total short-term investments, Estimated Fair Value	$55,151	$80,252

ShortTerm_Investments_Addition

Short-Term Investments - Additional Information (Detail) (USD $)	Sep. 26, 2014
In Thousands, unless otherwise specified
Investments, Debt and Equity Securities [Abstract]	'
Available-for-sale securities in a material unrealized loss position	$0

Derivative_and_Hedgiing_Activi1

Derivative and Hedgiing Activities Derivative and Hedging Activities (Details) (Foreign Exchange Forward [Member], Not Designated as Hedging Instrument [Member], USD $)	Sep. 26, 2014	Dec. 31, 2013	Sep. 26, 2014	Dec. 31, 2013	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
In Thousands, unless otherwise specified	Prepaid Expenses and Other Current Assets [Member]	Prepaid Expenses and Other Current Assets [Member]	Accrued Liabilities [Member]	Accrued Liabilities [Member]	Other Income [Member]	Other Income [Member]	Other Income [Member]	Other Income [Member]
Derivatives, Fair Value [Line Items]	'	'	'	'	'	'	'	'
Foreign currency contracts	$19	$196	'	'	'	'	'	'
Foreign currency contracts	'	'	-331	-195	'	'	'	'
Gain (loss) recorded in other income (expense), net	'	'	'	'	($95)	($157)	($201)	$658

Fair_Value_Measurements_Financ

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value Based on Three-Tier Fair Value Hierarchy (Detail) (USD $)	Sep. 26, 2014		Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Nonrecurring	$0		'
Liabilities, Fair Value Disclosure, Nonrecurring	0		'
Level 1 [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	7,393,000		55,022,000
Total liabilities measured and recorded at fair value	0		0
Level 2 [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	55,170,000		76,440,000
Total liabilities measured and recorded at fair value	331,000		195,000
Level 3 [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Total liabilities measured and recorded at fair value	0		0
Estimate of Fair Value Measurement [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	62,563,000		131,462,000
Total liabilities measured and recorded at fair value	331,000		195,000
Cash equivalents [Member] | Level 1 [Member] | Money market funds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	4,292,000		51,014,000
Cash equivalents [Member] | Level 2 [Member] | Money market funds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Cash equivalents [Member] | Level 3 [Member] | Money market funds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Cash equivalents [Member] | Estimate of Fair Value Measurement [Member] | Money market funds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	4,292,000		51,014,000
Short-term investments [Member] | Level 1 [Member] | State, municipal and local government agencies bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Short-term investments [Member] | Level 1 [Member] | Corporate bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Short-term investments [Member] | Level 1 [Member] | Commercial paper [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Short-term investments [Member] | Level 1 [Member] | U.S. federal government bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	'		4,008,000
Short-term investments [Member] | Level 2 [Member] | State, municipal and local government agencies bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	25,714,000		40,449,000
Short-term investments [Member] | Level 2 [Member] | Corporate bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	26,138,000		33,496,000
Short-term investments [Member] | Level 2 [Member] | Commercial paper [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	3,299,000		2,299,000
Short-term investments [Member] | Level 2 [Member] | U.S. federal government bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Short-term investments [Member] | Level 3 [Member] | State, municipal and local government agencies bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Short-term investments [Member] | Level 3 [Member] | Corporate bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Short-term investments [Member] | Level 3 [Member] | Commercial paper [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Short-term investments [Member] | Level 3 [Member] | U.S. federal government bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		0
Short-term investments [Member] | Estimate of Fair Value Measurement [Member] | State, municipal and local government agencies bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	25,714,000		40,449,000
Short-term investments [Member] | Estimate of Fair Value Measurement [Member] | Corporate bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	26,138,000		33,496,000
Short-term investments [Member] | Estimate of Fair Value Measurement [Member] | Commercial paper [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	3,299,000		2,299,000
Short-term investments [Member] | Estimate of Fair Value Measurement [Member] | U.S. federal government bonds [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0		4,008,000
Prepaids and other current assets [Member] | Level 1 [Member] | Foreign exchange forward contracts [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0	[1]	0	[1]
Prepaids and other current assets [Member] | Level 2 [Member] | Foreign exchange forward contracts [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	19,000	[1]	196,000	[1]
Prepaids and other current assets [Member] | Level 3 [Member] | Foreign exchange forward contracts [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	0	[1]	0	[1]
Prepaids and other current assets [Member] | Estimate of Fair Value Measurement [Member] | Foreign exchange forward contracts [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	19,000	[1]	196,000	[1]
Other Long-term Investments [Member] | Equity Securities [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	3,101,000		'
Other Long-term Investments [Member] | Level 1 [Member] | Equity Securities [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total assets measured and recorded at fair value	3,101,000		'
Accrued Liabilities [Member] | Level 1 [Member] | Foreign exchange forward contracts [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total liabilities measured and recorded at fair value	0	[1]	0	[1]
Accrued Liabilities [Member] | Level 2 [Member] | Foreign exchange forward contracts [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total liabilities measured and recorded at fair value	331,000	[1]	195,000	[1]
Accrued Liabilities [Member] | Level 3 [Member] | Foreign exchange forward contracts [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total liabilities measured and recorded at fair value	0	[1]	0	[1]
Accrued Liabilities [Member] | Estimate of Fair Value Measurement [Member] | Foreign exchange forward contracts [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Total liabilities measured and recorded at fair value	$331,000	[1]	$195,000	[1]
[1]	Derivative assets and liabilities represent forward currency exchange contracts. The Company enters into these contracts to minimize the short-term impact of foreign currency exchange rates fluctuations primarily from trade and inter-company receivables and payables.

Balance_Sheet_Components_Accou

Balance Sheet Components - Accounts Receivable, Net, Prepaid Expenses and Other Current Assets, Inventories, Property and Equipment, Net (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounts receivable, net:	'	'
Accounts receivable	$81,988	$83,266
Less: allowances for doubtful accounts, returns and discounts	-6,348	-8,214
Accounts receivable, net	75,640	75,052
Inventories:	'	'
Raw materials	1,805	2,389
Work-in-process	1,780	976
Finished goods	28,927	33,561
Total inventories, net	32,512	36,926
Property and equipment, net:	'	'
Furniture and fixtures	8,796	8,227
Machinery and equipment	117,765	114,178
Leasehold improvements	8,386	7,888
Property and equipment, gross	134,947	130,293
Less: accumulated depreciation and amortization	-104,133	-95,348
Property and equipment, net	$30,814	$34,945

Goodwill_and_Identified_Intang2

Goodwill and Identified Intangible Assets - Changes in Carrying Amount of Goodwill (Detail) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Balance at beginning of period	$198,022
Foreign currency translation adjustment	-15
Balance at end of period	$198,007

Goodwill_and_Identified_Intang3

Goodwill and Identified Intangible Assets - Summary of Goodwill and Identified Intangible Assets (Detail) (USD $)

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Sep. 26, 2014

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Sep. 26, 2014

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Sep. 26, 2014

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Sep. 26, 2014

In Thousands, unless otherwise specified

Developed core technology [Member]

Developed core technology [Member]

Developed core technology [Member]

Developed core technology [Member]

Customer relationships/contracts [Member]

Customer relationships/contracts [Member]

Customer relationships/contracts [Member]

Customer relationships/contracts [Member]

Trademarks and tradenames [Member]

Trademarks and tradenames [Member]

Trademarks and tradenames [Member]

Trademarks and tradenames [Member]

Maintenance agreements and related relationships [Member]

Maintenance agreements and related relationships [Member]

Maintenance agreements and related relationships [Member]

Maintenance agreements and related relationships [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Finite-Lived Intangible Assets [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Useful Life

'

'

'

'

'4 years

'6 years

'

'

'5 years

'6 years

'

'

'4 years

'5 years

'

'

'6 years

'7 years

Gross Carrying Amount

$221,704

$221,704

$136,145

$136,145

'

'

$67,098

$67,098

'

'

$11,361

$11,361

'

'

$7,100

$7,100

'

'

Accumulated Amortization

-208,964

-190,585

-134,731

-121,681

'

'

-57,568

-53,772

'

'

-11,361

-10,565

'

'

-5,304

-4,567

'

'

Total future amortization expense

$12,740

$31,119

$1,414

$14,464

'

'

$9,530

$13,326

'

'

$0

$796

'

'

$1,796

$2,533

'

'

Goodwill_and_Identified_Intang4

Goodwill and Identified Intangible Assets - Amortization Expense for Identifiable Purchased Intangible Assets (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Acquired Finite-Lived Intangible Assets [Line Items]	'	'	'	'
Total amortization expense	$5,512	$6,764	$18,378	$20,569
Included in cost of revenue [Member]	'	'	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'	'	'
Total amortization expense	3,851	4,763	13,049	14,470
Included in operating expenses [Member]	'	'	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'	'	'
Total amortization expense	$1,661	$2,001	$5,329	$6,099

Goodwill_and_Identified_Intang5

Goodwill and Identified Intangible Assets - Estimated Future Amortization Expense of Purchased Intangible Assets (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
2014 (remaining 3 months)	$2,141	'
2015	6,502	'
2016	4,097	'
Total future amortization expense	12,740	31,119
Product cost of revenue [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
2014 (remaining 3 months)	695	'
2015	719	'
2016	0	'
Total future amortization expense	1,414	'
Operating Expenses [Member]	'	'
Acquired Finite-Lived Intangible Assets [Line Items]	'	'
2014 (remaining 3 months)	1,446	'
2015	5,783	'
2016	4,097	'
Total future amortization expense	$11,326	'

Restructuring_and_Related_Char2

Restructuring and Related Charges - Activities in Restructuring Accrual (Detail) (USD $)

3 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Dec. 31, 2013

Sep. 26, 2014

Sep. 26, 2014

Sep. 26, 2014

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Harmonic Two Thousand And Thirteen Restructuring [Member]

Harmonic Two Thousand And Thirteen Restructuring [Member]

Harmonic Two Thousand And Thirteen Restructuring [Member]

Harmonic Two Thousand And Thirteen Restructuring [Member]

Harmonic Two Thousand And Thirteen Restructuring [Member]

Harmonic Two Thousand And Thirteen Restructuring [Member]

Product cost of revenue [Member]

Product cost of revenue [Member]

Product cost of revenue [Member]

Product cost of revenue [Member]

Operating Expense [Member]

Operating Expense [Member]

Operating Expense [Member]

Operating Expense [Member]

Severance [Member]

Termination of a research and development project [Member]

Excess Facilities [Member]

Restructuring Cost and Reserve [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Restructuring and Related Cost, Incurred Cost

$403,000

$583,000

$915,000

$1,455,000

'

'

'

'

'

'

$15,000

$324,000

$94,000

$530,000

$388,000

$259,000

$821,000

$925,000

Restructuring Reserve [Roll Forward]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Beginning Balance

'

'

'

'

179,000

'

'

179,000

0

0

'

'

'

'

'

'

'

'

Restructuring and related charges

388,000

259,000

821,000

925,000

924,000

1,455,000

2,200,000

829,000

63,000

32,000

'

'

'

'

'

'

'

'

Adjustments to restructuring provisions

'

'

'

'

-9,000

'

'

-9,000

0

0

'

'

'

'

'

'

'

'

Cash payments

'

'

'

'

-747,000

'

'

-715,000

0

-32,000

'

'

'

'

'

'

'

'

Ending Balance

'

'

'

'

$347,000

'

$179,000

$284,000

$63,000

$0

'

'

'

'

'

'

'

'

Restructuring_and_Related_Char3

Restructuring and Related Charges - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended		12 Months Ended	1 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 26, 2014	Sep. 27, 2013	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2013
					Harmonic 2013 Restructuring [Member]	Harmonic 2013 Restructuring [Member]	Harmonic 2013 Restructuring [Member]	Harmonic 2013 Restructuring [Member]	HFC business [Member]	HFC business [Member]
						Employees
Restructuring Cost and Reserve [Line Items]	'	'	'	'	'	'	'	'	'	'
Restructuring charges	$388,000	$259,000	$821,000	$925,000	'	$924,000	$1,455,000	$2,200,000	$600,000	'
Restructuring Costs	'	'	'	'	403,000	915,000	'	'	'	'
Restructuring Reserve	'	'	'	'	$347,000	$347,000	'	$179,000	'	$13,000
Number of positions eliminated	'	'	'	'	'	25	'	'	'	'

Credit_Facilities_Additional_I

Credit Facilities - Additional Information (Detail) (USD $)	9 Months Ended	8 Months Ended				9 Months Ended			4 Months Ended
	Sep. 26, 2014	Aug. 21, 2014	Sep. 26, 2014	Sep. 26, 2014	Sep. 26, 2014	Sep. 26, 2014	Sep. 26, 2014	Sep. 26, 2014	Dec. 31, 2014
		LIBOR [Member]	LIBOR [Member]	Standby letters of credit [Member]	Line of credit facility [Member]	Minimum [Member]	Minimum [Member]	Maximum [Member]	Subsequent Event [Member]
							LIBOR [Member]	LIBOR [Member]	LIBOR [Member]
Debt Instrument [Line Items]	'	'	'	'	'	'	'	'	'
Line of Credit Facility, Covenant, Certain Assets to Certain Liabilities Less Deferred Revenue Ratio	3.26	'	'	'	'	1.75	'	'	'
Maximum borrowing capacity under bank line of credit facility	$10,000,000	'	'	$200,000	'	'	'	'	'
Line of Credit Facility, Remaining Borrowing Capacity	'	'	'	'	9,800,000	'	'	'	'
Line of Credit Facility, Covenant Terms	'3.26 to 1	'	'	'	'	'	'	'	'
Bank line of credit facility, maturity date	31-Dec-14	'	'	'	'	'	'	'	'
Unrestricted Cash Cash Equivalents And Short Term Investments To Current Liabilities Ratio	'Harmonic to maintain a ratio of unrestricted cash, accounts receivable and short term investments to current liabilities (less deferred revenue) of at least 1.75 to 1.00.	'	'	'	'	'	'	'	'
Line of Credit LIBOR margin	'	1.75%	'	'	'	'	1.50%	1.65%	1.50%
Borrowings under bank line of credit facility	$0	'	'	'	'	'	'	'	'
Bank's Prime Rate	3.25%	'	'	'	'	'	'	'	'
Annualized rate of LIBOR	'	'	0.15%	'	'	'	'	'	'
LIBOR rate duration	'one month borrowing period at September 26, 2014	'	'	'	'	'	'	'	'
Credit facility collateral	'Borrowings are not collateralized	'	'	'	'	'	'	'	'
Covenants under the line of credit facility	'As of September 26, 2014, Harmonic was in compliance with the covenants under the line of credit facility	'	'	'	'	'	'	'	'

Employee_Benefit_Plans_Summary

Employee Benefit Plans - Summary of Company's Stock Option and Restricted Stock Unit Activity (Detail) (USD $)	9 Months Ended
	Sep. 26, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares Available for Grant, Beginning balance	8,752,000
Shares Available for Grant, Authorized	350,000
Shares Available for Grant, Granted	-3,477,000
Shares Available for Grant, Options exercised	0
Shares Available for Grant, Shares released	0
Shares Available for Grant, Forfeited or cancelled	1,753,000
Shares Available for Grant, Ending balance	7,378,000
Restricted Stock Units Outstanding [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Number of Units, Beginning balance	3,018,000
Number of Shares, Authorized	0
Number of Units, Granted	1,352,000
Number of Units, exercised	0
Number of Units, Shares released	-1,589,000
Number of Units, Forfeited or cancelled	-232,000
Number of Units, Ending balance	2,549,000
Weighted Average Grant Date Fair Value, Beginning balance	6.34
Weighted Average Grant Date Fair Value, Authorized	0
Estimated weighted average fair value per share at purchase date	6.55
Weighted Average Grant Date Fair Value, Exercised	0
Weighted Average Grant Date Fair Value, Shares released	6.32
Weighted Average Grant Date Fair Value, Forfeited or cancelled	6.13
Weighted Average Grant Date Fair Value, Ending balance	6.49
Stock Options Outstanding [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Number of Shares, Beginning balance	7,885,000
Number of Shares, Authorized	0
Number of Shares, Granted	1,450,000
Number of Shares, Options exercised	-329,000
Number of Shares, Forfeited or cancelled	-1,592,000
Number of Shares, Ending balance	7,414,000
Weighted Average Exercise Price, Beginning balance	6.92
Weighted Average Exercise Price, Authorized	0
Weighted Average Exercise Price, Granted	6.52
Weighted Average Exercise Price, Options exercised	4.91
Weighted Average Exercise Price, Forfeited or cancelled	8.15
Weighted Average Exercise Price, Ending balance	6.67

Employee_Benefit_Plans_Summary1

Employee Benefit Plans - Summary of Stock Options Outstanding (Detail) (Stock Options Outstanding [Member], USD $)	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 26, 2014
Stock Options Outstanding [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Number of Shares, Vested and expected to vest	7,095
Weighted Average Exercise Price, Vested and expected to vest	$6.68
Weighted Average Remaining Contractual Term (Years), Vested and expected to vest	'3 years 7 months 13 days
Aggregate Intrinsic Value, Vested and expected to vest	$3,118
Number of Shares, Exercisable	4,760
Weighted Average Exercise Price, Exercisable	$6.84
Weighted Average Remaining Contractual Term (Years), Exercisable	'2 years 6 months
Aggregate Intrinsic Value, Exercisable	$2,519

Employee_Benefit_Plans_Summary2

Employee Benefit Plans - Summary of Restricted Stock Units Outstanding (Detail) (Restricted Stock Units Outstanding [Member], USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014
Restricted Stock Units Outstanding [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Number of Shares Underlying Restricted Stock Units	2,365
Weighted Average Remaining Vesting Period (Years)	'0 years 8 months 15 days
Aggregate Fair Value	$15,114

Employee_Benefit_Plans_Additio

Employee Benefit Plans - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended				0 Months Ended		3 Months Ended	9 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013	Jul. 29, 2014	Aug. 14, 2013	Sep. 26, 2014	Sep. 26, 2014	Sep. 26, 2014
					Employee Stock Purchase Plan [Member]	Employee Stock Purchase Plan [Member]	Employee Stock Purchase Plan [Member]	Employee Stock Purchase Plan [Member]	Employee Stock Purchase Plan [Member]	Minimum [Member]	Maximum [Member]
										Employee Stock Purchase Plan [Member]	Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Intrinsic value of options exercised	$300,000	$1,100,000	$700,000	$2,000,000	'	'	'	'	'	'	'
Percentage of fair market value of Common Stock to purchase shares	'	'	'	'	85.00%	'	'	'	85.00%	'	'
Employee Stock Purchase Plan Payroll Deductions	'	'	'	'	'	'	'	'	'	1.00%	10.00%
Percentage of shares available to fund for ESPP	'	'	'	'	'	53.00%	'	'	'	'	'
Refunded percentage of employee contribution	'	'	'	'	'	47.00%	'	'	'	'	'
Increase in authorized shares for ESPP	'	'	350,000	'	'	'	1,000,000	1,000,000	'	'	'
Discretionary contributions of plan	'	'	25.00%	'	'	'	'	'	'	'	'
Percent of employees' gross pay eligible for matching	'	'	4.00%	'	'	'	'	'	'	'	'
Maximum contribution amount per participant	'	'	1,000	'	'	'	'	'	'	'	'
Contributions in period	'	'	$354,000	$387,000	'	'	'	'	'	'	'
Defined contribution plan description	'	'	'Harmonic has a retirement/savings plan which qualifies as a thrift plan under Section 401(k) of the Internal Revenue Code. This plan allows participants to contribute up to the applicable Internal Revenue Code limitations under the plan. Harmonic has made discretionary contributions to the plan of 25% of the first 4% contributed by eligible participants, up to a maximum contribution per participant of $1,000 per year.	'	'	'	'	'	'	'	'

StockBased_Compensation_Summar

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock-based compensation	'	'	$12,720	$11,953
Total stock-based compensation in operating expense	3,740	3,340	10,969	10,028
Total stock-based compensation	4,352	3,945	12,720	11,866
Product cost of revenue [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock-based compensation	612	605	1,751	1,838
Research and development expense [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock-based compensation	1,219	1,076	3,589	3,400
Selling, general and administrative expense [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock-based compensation	$2,521	$2,264	$7,380	$6,628

StockBased_Compensation_Valuat

Stock-Based Compensation - Valuation Assumptions for Stock Options (Detail)	9 Months Ended	3 Months Ended		9 Months Ended		6 Months Ended		3 Months Ended
	Sep. 26, 2014	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013	Jun. 30, 2013	Jun. 30, 2014	Sep. 26, 2014
	Employee Stock Purchase Plan [Member]	Stock Options [Member]	Stock Options [Member]	Stock Options [Member]	Stock Options [Member]	Purchase Period June 30, 2013 [Member]	Purchase Period June 30, 2014 [Member]	Purchase Period December 31, 2014 [Member]
						Employee Stock Purchase Plan [Member]	Employee Stock Purchase Plan [Member]	Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'	'
Expected term (years)	'	'4 years 8 months 13 days	'4 years 8 months 13 days	'4 years 8 months 13 days	'4 years 8 months 13 days	'5 months 27 days	'6 months	'6 months
Volatility	'	40.00%	46.00%	40.00%	51.00%	30.00%	28.00%	33.00%
Risk-free interest rate	'	1.80%	1.50%	1.70%	0.80%	0.20%	0.10%	0.10%
Expected dividends	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Jul. 29, 2014

Aug. 14, 2013

Sep. 26, 2014

Sep. 26, 2014

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Stock Options [Member]

Stock Options [Member]

Stock Options [Member]

Stock Options [Member]

Employee Stock Purchase Plan [Member]

Employee Stock Purchase Plan [Member]

Employee Stock Purchase Plan [Member]

Employee Stock Purchase Plan [Member]

Restricted Stock Units Outstanding [Member]

Restricted Stock Units Outstanding [Member]

Restricted Stock Units Outstanding [Member]

Restricted Stock Units Outstanding [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected dividend yield

'

'

'

'

0.00%

0.00%

0.00%

0.00%

'

'

'

0.00%

'

'

'

'

Weighted-average fair value per share of options granted

$2.48

$3.02

$2.36

$2.51

'

'

'

'

'

'

'

'

'

'

'

'

Fair value of options vested

$600,000

$800,000

$2,600,000

$2,800,000

'

'

'

'

'

'

'

'

'

'

'

'

Total realized tax benefit

'

'

194,000

0

'

'

'

'

'

'

'

'

'

'

'

'

Issuance of restricted stocks fair value

'

'

'

'

'

'

'

'

'

'

'

'

2,700,000

2,800,000

10,000,000

10,200,000

Discount percentage on purchase of stock

'

'

'

'

'

'

'

'

'

'

15.00%

'

'

'

'

'

Fair Value of stock purchase rights percentage of call option

'

'

'

'

'

'

'

'

'

'

85.00%

'

'

'

'

'

Value of stock purchase rights percentage of put option

'

'

'

'

'

'

'

'

'

'

15.00%

'

'

'

'

'

Weighted-average fair value per share other than option granted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$6.55

'

Increase in authorized shares for ESPP

'

'

350,000

'

'

'

'

'

1,000,000

1,000,000

'

'

'

'

'

'

Total unamortized stock-based compensation cost related to unvested stock options and restricted stock units

$17,100,000

'

$17,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Remaining weighted-average amortization period

'

'

'1 year 8 months 15 days

'

'

'

'

'

'

'

'

'

'

'

'

'

StockBased_Compensation_Employ

Stock-Based Compensation - Employee Stock Purchase Plan (Detail) (Employee Stock Purchase Plan [Member], USD $)	9 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended
	Sep. 26, 2014	Jun. 30, 2014	Jun. 30, 2013	Sep. 26, 2014	Dec. 31, 2014
		Purchase Period June 30, 2014 [Member]	Purchase Period June 30, 2013 [Member]	Purchase Period December 31, 2014 [Member]	Scenario, Forecast [Member]
					Purchase Period June 30, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'
Expected term (years)	'	'6 months	'5 months 27 days	'6 months	'
Volatility	'	28.00%	30.00%	33.00%	'
Risk-free interest rate	'	0.10%	0.20%	0.10%	'
Expected dividends	0.00%	0.00%	0.00%	0.00%	'
Estimated weighted average fair value per share at purchase date	'	$1.70	$1.23	'	$1.84

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Income Tax Disclosure [Abstract]	'	'	'	'
Loss from continuing operations before income taxes	($3,752)	($2,278)	($19,594)	($21,955)
Provision for (benefit from) income taxes	($4,830)	($38,953)	$21,800	($45,723)
Effective income tax rate	128.70%	1710.00%	-111.30%	208.30%

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended			9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Jun. 27, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Income Tax Contingency [Line Items]	'	'	'	'	'
Federal statutory income tax rate	'	'	'	35.00%	35.00%
Valuation Allowance, Deferred Tax Asset, Change in Amount	$4.20	$24.50	'	$28.70	'
Net tax benefit associated with release of tax reserves for uncertain tax positions	'	'	'	8.5	38.4
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	8.5	'	38.4	'	'
Unrecognized tax benefits that would impact the provision for income taxes	16.8	'	'	16.8	'
Interest and possible penalties related to uncertain tax positions	0.3	'	'	0.3	'
Potential decrease over the next twelve months for uncertain tax positions due to expiration of applicable statute of limitations	$0.60	'	'	$0.60	'
SWITZERLAND	'	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'	'
Income Tax Holiday, Description	'	'	'	'The Company's operations in Switzerland are subject to a reduced tax rate under the Switzerland tax holiday which requires various thresholds of investment and employment in Switzerland. The Company has met these various thresholds and the Switzerland tax holiday is effective through the end of 2018.	'

Income_Loss_Per_Share_Numerato

Income (Loss) Per Share - Numerators and Denominators of Basic and Diluted Net Income (Loss) Per Share Computations (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Numerator:	'	'	'	'
Income (loss) from continuing operations	$1,078	$36,675	($41,394)	$23,768
Income from discontinued operations	0	91	0	15,619
Net income (loss)	$1,078	$36,766	($41,394)	$39,387
Denominator:	'	'	'	'
Basic	90,618	101,144	94,113	108,695
Effect of dilutive securities from stock options, restricted stock units and ESPP	1,182	1,579	0	1,184
Diluted	91,800	102,723	94,113	109,879
Basic net income (loss) per share from:	'	'	'	'
Continuing operations	$0.01	$0.36	($0.44)	$0.22
Discontinued operations	$0	$0	$0	$0.14
Net income (loss)	$0.01	$0.36	($0.44)	$0.36
Diluted net income (loss) per share from:	'	'	'	'
Continuing operations	$0.01	$0.36	($0.44)	$0.22
Discontinued operations	$0	$0	$0	$0.14
Net Income (loss)	$0.01	$0.36	($0.44)	$0.36

Income_Loss_Per_Share_Antidilu

Income (Loss) Per Share - Anti-dilutive Securities (Detail)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Earnings Per Share [Abstract]	'	'	'	'
Potentially dilutive equity awards outstanding	5,196	6,144	9,321	10,681

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	Sep. 26, 2014	Jun. 29, 2012	Oct. 31, 2011
		Patents	Patents
Contingencies And Commitments [Line Items]	'	'	'
Future sublease income from Aurora	$300,000	'	'
Non-cancelable purchase commitments	17,600,000	'	'
Maximum amount of potential future payments under the company's financial guarantees	200,000	'	'
Infringements of number of patents held	'	1	2
Israel [Member]	'	'	'
Contingencies And Commitments [Line Items]	'	'	'
Guarantees related to rent obligations	400,000	'	'
Indemnification [Member]	'	'	'
Contingencies And Commitments [Line Items]	'	'	'
Accrual for indemnification provisions	$0	'	'

Commitments_and_Contingencies_2

Commitments and Contingencies - Future Minimum Lease Payments Under Non-cancelable Operating Leases (Detail) (USD $)	Sep. 26, 2014
In Thousands, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]	'
2014 (remaining three months)	$2,622
2015	10,307
2016	8,600
2017	7,795
2018	7,650
Thereafter	13,731
Total	$50,705

Commitments_and_Contingencies_3

Commitments and Contingencies - Summary of Warranty Accrual Included in Accrued Liabilities (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Commitments and Contingencies Disclosure [Abstract]	'	'	'	'
Balance at beginning of period	$3,532	$3,228	$3,606	$4,292
Transfer to Aurora as part of the sale of discontinued operations	0	0	0	-939
Accrual for current period warranties	2,028	1,991	5,383	5,333
Warranty costs incurred	-1,629	-1,705	-5,058	-5,172
Balance at end of period	$3,931	$3,514	$3,931	$3,514

Stockholders_Equity_Components

Stockholders' Equity - Components of Accumulated Other Comprehensive Loss (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Equity [Abstract]	'	'
Foreign currency translation adjustments	($682)	($242)
Unrealized gain on investments	-288	33
Accumulated Other Comprehensive Loss	($970)	($209)

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	0 Months Ended	9 Months Ended	12 Months Ended	23 Months Ended
In Millions, except Per Share data, unless otherwise specified	Apr. 24, 2012	Sep. 26, 2014	Dec. 31, 2013	Mar. 28, 2014
Equity [Abstract]	'	'	'	'
Authorized stock repurchase value	$25	'	$220	'
Increase in stock repurchase program	'	80	195	'
Stock Repurchased and Retired During Period, Shares	'	'	'	36.3
Weighted average purchase price per share	'	'	'	$6.19
Common stock repurchased and retired, aggregate value	'	'	'	224.6
Remaining authorized repurchase amount	'	'	'	$75.40

Subsequent_Event_Details

Subsequent Event (Details) (Encoding Inc [Member], Subsequent Event [Member])	Oct. 22, 2014
Encoding Inc [Member] | Subsequent Event [Member]	'
Subsequent Event [Line Items]	'
Noncontrolling Interest, Ownership Percentage by Parent	18.40%