Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Oct. 03, 2015
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying Consolidated Financial Statements include the accounts of Lattice and its subsidiaries after the elimination of all intercompany balances and transactions. Certain balances in prior fiscal years have been reclassified to conform to the presentation adopted in the current year. Interest expense has been reported separately from Other (expense) income, net.
Cash Equivalents	We consider all investments that are readily convertible into cash and have original maturities of three months or less to be cash equivalents. Cash equivalents consist primarily of highly liquid investments in time deposits or money market accounts and are carried at cost.
Marketable Securities	We account for marketable securities as available-for-sale investments, as defined by U.S. GAAP, and record unrealized gains or losses to Accumulated other comprehensive loss on our Consolidated Balance Sheets, unless losses are considered other than temporary, in which case, those are recorded directly to the Consolidated Statements of Operations and Statements of Comprehensive (Loss) Income.
Fair Value of Financial Instruments	Fair Value of Financial Instruments We invest in various financial instruments including corporate and government bonds, notes, and commercial paper. In the past we have also invested in auction rate securities. We value these instruments at their fair value and monitor the 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, we record an impairment charge and establish a new carrying value. We assess other than temporary impairment of marketable securities in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 820, “Fair Value Measurements.” The framework under the provisions of ASC 820 establishes three levels of inputs that may be used to measure fair value. Each level of input has different levels of subjectivity and difficulty involved in determining fair value.
Foreign Exchange and Translation of Foreign Currencies	Foreign Exchange and Translation of Foreign Currencies We have international subsidiary and branch operations. In addition, a portion of our silicon wafer and other purchases are denominated in Japanese yen, we bill certain Japanese customers in yen and collect a Japanese consumption tax refund in yen. Gains or losses from foreign exchange rate fluctuations on balances denominated in foreign currencies are reflected in Other (expense) income, net. Realized and unrealized gains or losses on foreign currency transactions were not significant for the periods presented. We translate accounts denominated in foreign currencies in accordance with ASC 830, “Foreign Currency Matters,” using the current rate method under which asset and liability accounts are translated at the current rate, while stockholders' equity accounts are translated at the appropriate historical rates, and revenue and expense accounts are translated at average monthly exchange rates. Translation adjustments related to the consolidation of foreign subsidiary financial statements are reflected in Accumulated other comprehensive loss in Stockholders' equity.
Derivative Financial Instruments	Derivative Financial Instruments We mitigate foreign currency exchange rate risk by entering into foreign currency forward exchange contracts. At October 3, 2015 and January 3, 2015, we had open foreign exchange contracts of $1.7 million and $4.2 million, respectively. One contract outstanding at October 3, 2015 settled in October 2015, and three contracts will settle in June 2016. Although these hedges mitigate our foreign currency exchange rate exposure from an economic perspective, they were not designated as "effective" hedges under GAAP and as such are adjusted to fair value through Other (expense) income, net, with an impact of less than $0.1 million for the periods reported in the Consolidated Statements of Operations. We do not hold or issue derivative financial instruments for trading or speculative purposes.
Concentration Risk	Concentration Risk Potential exposure to concentration risk may impact revenue, trade receivables, marketable securities, and supply of wafers for our new products. Customer concentration risk may impact revenue. Our top five end customers constituted approximately 31% of our revenue for the third quarter of fiscal 2015, compared to approximately 41% for the third quarter of fiscal 2014. Our top five end customers constituted approximately 33% of our revenue for the first nine months of fiscal 2015, compared to approximately 46% for the first nine month of fiscal 2014. Our largest end customer accounted for approximately 9% of total revenue in the third quarter of fiscal 2015 and 11% of total revenue in the first nine months of fiscal 2015. Our two largest end customers accounted for approximately 18% and 10% of total revenue, respectively, in the third quarter of fiscal 2014 and 21% and 12% of total revenue, respectively, in the first nine months of fiscal 2014. No other customers accounted for more than 10% of total revenue during these periods. Sales through distributors have historically accounted for a significant portion of our total revenue. Revenue attributable to resale of products by our sell-through distributors for the third quarter of fiscal 2015 and fiscal 2014 was 46% and 51%, respectively. Revenue attributable to resale of products by our sell-through distributors for the first nine months of fiscal 2015 and fiscal 2014 was 45% and 44%, respectively. Concentration of credit risk with respect to trade receivables is mitigated by our credit and collection process including active management of collections, credit limits, routine credit evaluations for essentially all customers and secure transactions with letters of credit or advance payments where appropriate. Accounts receivable do not bear interest and are shown net of allowances for doubtful accounts of $0.9 million and $0.9 million at October 3, 2015 and January 3, 2015, respectively. We regularly review our allowance for doubtful accounts and the aging of our accounts receivable. Write-offs for uncollected trade receivables have not been significant to date. We place our investments primarily through one financial institution and mitigate the concentration of credit risk by limiting the maximum portion of the investment portfolio which may be invested in any one instrument. Our investment policy defines approved credit ratings for investment securities. Investments on-hand in marketable securities consisted primarily of money market instruments, “AA” or better corporate notes and bonds and commercial paper, and U.S. government agency obligations. See Note 5 for a discussion of the liquidity attributes of our marketable securities. We rely on a limited number of foundries for our wafer purchases including Fujitsu Limited, Seiko Epson Corporation, Taiwan Semiconductor Manufacturing Company, Ltd, and United Microelectronics Corporation.
Revenue Recognition and Deferred Income	Revenue Recognition and Deferred Income Product Revenue We sell our products directly to end customers, through a network of independent manufacturers' representatives, and indirectly through a network of independent sell-in and sell-through distributors. Distributors provide periodic data regarding the product, price, quantity, and end customer when products are resold, as well as the quantities of our products they still have in stock. Revenue from sales to original equipment manufacturers ("OEMs") and sell-in distributors is generally recognized upon shipment. Reserves for sell-in stock rotations, where applicable, are estimated based primarily on historical experience and provided for at the time of shipment. Revenue from sales by our sell-through distributors is recognized at the time of reported resale. Under both types of revenue recognition, persuasive evidence of an arrangement exists, the price is fixed or determinable, title has transferred, collection of resulting receivables is reasonably assured, and there are no remaining customer acceptance requirements and no remaining significant performance obligations. Orders from our sell-through distributors are initially recorded at published list prices; however, for a majority of our sales, the final selling price is determined at the time of resale and in accordance with a distributor price agreement. In certain circumstances, we allow sell-through distributors to return unsold products. At times, we protect our sell-through distributors against reductions in published list prices. For these reasons, we do not recognize revenue until products are resold by sell-through distributors to an end customer. For sell-through distributors, at the time of shipment to distributors, we (a) record Accounts receivable at published list price since there is a legally enforceable obligation from the distributor to pay us currently for product delivered, (b) relieve inventory for the carrying value of goods shipped since legal title has passed to the distributor, and (c) record deferred revenue and deferred cost of sales in Deferred income and allowances on sales to sell-through distributors in the liability section of our Consolidated Balance Sheets. The final price is set at the time of resale and is determined in accordance with a distributor price agreement. Revenue and cost of sales to sell-through distributors are deferred until either the product is resold by the distributor or, in certain cases, return privileges terminate, at which time Revenue and Cost of products sold are reflected in Net (loss) income, and Accounts receivable, net are adjusted to reflect the final selling price. We must use estimates and apply judgment to reconcile sell-through distributors' reported inventories to their activities. Errors in our estimates or judgments could result in inaccurate reporting of our Revenue, Cost of products sold, Deferred income and allowances on sales to sell-through distributors, and Net (loss) income. Licensing and Services Revenue Our licensing and services revenue is comprised of revenue from our intellectual property ("IP") core licensing activity, patent monetization activities, device management system and remote support services, and royalty and adopter fee revenue from our standards activities. These activities are complementary to our product sales and help us monetize our intellectual property and accelerate market adoption curves associated with our technology and standards. We enter into IP licensing agreements that generally provide licensees the right to incorporate our IP components into their products pursuant to terms and conditions that vary by licensee. Revenue earned under these agreements is classified as Licensing and services revenue. Our IP licensing agreements generally include multiple elements, which may include one or more off-the-shelf or customized IP licenses bundled with support services covering a fixed period of time, generally one year. If the different elements of a multiple-element arrangement qualify as separate units of accounting, we allocate the total arrangement consideration to each element based on relative selling price. Amounts allocated to off-the-shelf IP licenses are recognized at the time of sale provided the other conditions for revenue recognition have been met. Amounts allocated to the support services are deferred and recognized on a straight-line basis over the support period, generally one year. Certain licensing agreements provide for royalty payments based on agreed-upon royalty rates, which may be fixed or variable depending on the terms of the agreement. The amount of revenue we recognize is based on a specified time period or on the agreed-upon royalty rate multiplied by the number of units shipped by the customer. From time to time, we enter into IP licensing agreements that involve significant modification, customization or engineering services. Revenues derived from these contracts are accounted for using the percentage-of-completion method or completed contract method. The completed contract method is used for contracts where there is a risk of final acceptance by the customer or for short-term contracts. HDMI royalty revenue is determined by a contractual allocation formula agreed to by the members ("Founders") of the HDMI consortium. Evidence of an arrangement, as to HDMI royalty revenue, is deemed complete when all of the Founders agree on the royalty sharing formula.
Property and Equipment	Property and Equipment Property and equipment are stated at cost. Depreciation and amortization are computed using the straight-line method for financial reporting purposes over the estimated useful lives of the related assets, generally three to five years for equipment and software, one to three years for tooling and thirty years for buildings. Upon disposal of Property and equipment, the accounts are relieved of the costs and related accumulated depreciation and amortization, and resulting gains or losses are reflected in the Consolidated Statements of Operations for recognized gains and losses, or in the Consolidated Balance Sheets for deferred gains and losses. Repair and maintenance costs are expensed as incurred.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts and classification of assets, such as marketable securities, accounts receivable, inventory, goodwill (including the assessment of reporting unit), intangible assets, current and deferred income taxes, accrued liabilities (including restructuring charges and bonus arrangements), deferred income and allowances on sales to sell-through distributors, disclosure of contingent assets and liabilities at the date of the financial statements, anticipated amounts used in acquisition valuations and purchase accounting, and the reported amounts of revenue and expenses during the fiscal periods presented. Actual results could differ from those estimates.
New Accounting Pronouncements	New Accounting Pronouncements: In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The ASU will replace most existing revenue recognition guidance under U.S. GAAP when it becomes effective. While ASU 2014-09 was to be effective for annual periods and interim periods beginning after December 15, 2016, in August 2015, the FASB issued ASU 2015-14 deferring the effective date of ASU 2015-09 to periods beginning on or after December 15, 2017, with early adoption permitted for annual reporting periods beginning after December 15, 2016, and interim periods within that year. With the deferral, we intend to adopt ASU 2014-09 on December 31, 2017. The standard permits the use of either the retrospective or cumulative effect transition method. We are currently evaluating the impact of ASU 2014-09 on our consolidated financial statements and related disclosures and have not yet selected a transition method. In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis, which focuses on the consolidation evaluation for reporting organizations and requires the evaluation of whether or not certain legal entities should be consolidated. All legal entities are subject to reevaluation under the revised consolidation model. The new standard will become effective for us on January 3, 2016. Early adoption is permitted, including adoption in an interim period. We do not expect the adoption of this accounting standard update to impact our consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, Simplifying the Presentation of Debt Issuance Cost. The ASU requires debt issuance costs associated with a recognized debt liability to be presented on the balance sheet as a direct deduction from the carrying amount of the corresponding debt liability. This new guidance is effective for interim and annual reporting periods beginning after December 15, 2015, with early adoption permitted. An entity should apply the new guidance on a retrospective basis. We adopted this ASU effective with the first quarter of fiscal year 2015. In July 2015, the FASB issued ASU 2015-11, Simplifying the Measurement of Inventory. Under this ASU, inventory will be measured at the “lower of cost and net realizable value” and options that currently exist for “market value” will be eliminated. The ASU defines net realizable value as the “estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation.” No other changes were made to the current guidance on inventory measure-ment. ASU 2015-11 is effective for interim and annual periods beginning after December 15, 2016. Early application is permitted and should be applied prospectively. We do not expect the adoption of this accounting standard update to impact our consolidated financial statements. In September 2015, the FASB issued ASU 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments. This ASU eliminates the requirement to restate prior period financial statements for measurement period adjustments following a business combination. The new guidance requires that the cumulative impact of a measurement period adjustment (including the impact on prior periods) be recognized in the reporting period in which the adjustment is determined. The prior period impact of the adjustment should be either presented separately on the face of the income statement or disclosed in the notes. The guidance is effective for interim and annual periods beginning after December 15, 2015. Early application is permitted and should be applied prospectively. We do not expect the adoption of this accounting standard update to impact our consolidated financial statements.