The Company and Summary of Significant Accounting Policies	9 Months Ended
Oct. 01, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and Summary of Significant Accounting Policies	The Company and Summary of Significant Accounting Policies Quantenna Communications, Inc. (the “Company”) was incorporated in the State of Delaware on November 28, 2005. The Company designs, develops and markets advanced high-speed wireless communication solutions enabling wireless local area networking. The Company’s wireless communication solutions deliver high performance, speed, and reliability for wireless networks and devices. Reporting Calendar The Company prepares financial statements on a 52- or 53-week fiscal year that ends on the Sunday closest to December 31. Fiscal 2017 will have 52 weeks and fiscal 2016 had 53 weeks. In a 52-week year, each fiscal quarter consists of 13 weeks. Fiscal 2017 will end on December 31, 2017. Initial Public Offering On October 27, 2016, the Company’s registration statement on Form S-1 relating to its initial public offering (“IPO”) of its common stock was declared effective by the U.S. Securities and Exchange Commission (“SEC”) and the shares of its common stock began trading on the NASDAQ Global Select Market on October 28, 2016. The public offering price of the shares sold in the IPO was $16.00 per share. The IPO closed on November 2, 2016 and a second close occurred on November 25, 2016, pursuant to which the Company sold 6,775,466 shares of common stock, including the sale of 75,466 shares of common stock to the underwriters upon their exercise of their option to purchase additional shares. The Company received net proceeds of approximately $97.4 million, after underwriting discounts, commissions and offering expenses. Immediately prior to the consummation of the IPO, all outstanding shares of convertible preferred stock and preferred stock warrants were converted into common stock and common stock warrants, respectively. Unaudited Interim Financial Information The accompanying interim condensed consolidated financial statements and related disclosures are unaudited and in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the results of operations for the periods presented. The year-end condensed consolidated balance sheet data 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”). The condensed consolidated results of operations for the three and nine months ended October 1, 2017 are not necessarily indicative of the results to be expected for the full year or for any other future year or interim period. The accompanying condensed consolidated financial statements should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended January 1, 2017 filed with the SEC on March 1, 2017 (“2016 Annual Report on Form 10-K”). Use of Estimates Preparation of financial statements in conformity with US 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 reported amounts of revenue and expenses during the reporting periods covered by the financial statements and accompanying notes. Actual results could differ from those estimates. Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Significant Accounting Policies During the three and nine months ended October 1, 2017, there have been no changes in our significant accounting policies as described in the Company’s 2016 Annual Report on Form 10-K, except as discussed below: Stock-based compensation The Company measures and recognizes compensation expense for all stock-based awards made to employees, directors and non-employees, based on estimated fair values recognized using the straight-line method over the requisite service period. On January 1, 2017, the Company adopted the Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. Under this guidance, the Company elected the option to no longer apply a forfeiture rate to the stock-based compensation expense, but to record forfeitures when they occur, and, as a result, under the modified retrospective method of adoption the Company recorded an immaterial cumulative effect adjustment of $54,000 to the opening accumulated deficit on January 2, 2017. Marketable Securities Marketable securities consist primarily of highly liquid investments with maturities of greater than 90 days when purchased. We generally classify our marketable securities at the date of acquisition as available-for-sale. These securities are reported at fair value with the related unrealized gains and losses included in "Accumulated other comprehensive loss", a component of stockholders’ equity, net of tax. Any unrealized losses which are considered to be other-than-temporary impairments are recorded in "Other income (expense), net" in the Condensed Consolidated Statements of Operations. Realized gains (losses) on the sale of marketable securities are determined using the specific-identification method and recorded in "Other income (expense), net" in the Consolidated Statements of Operations. All of our available-for-sale investments are subject to a periodic impairment review. We record a charge to earnings when a decline in fair value is significantly below cost basis and judged to be other-than-temporary, or have other indicators of impairments. If the fair value of an available-for-sale investment is less than its amortized cost basis, an other-than-temporary impairment is triggered in circumstances where (1) we intend to sell the instrument, (2) it is more likely than not that we will be required to sell the instrument before recovery of its amortized cost basis or (3) a credit loss exists where we do not expect to recover the entire amortized cost basis of the instrument. If we intend to sell or it is more likely than not that we will be required to sell the available-for-sale investment before recovery of its amortized cost basis, we recognize an other-than temporary impairment charge equal to the entire difference between the investment's amortized cost basis and its fair value. Intangible Assets On September 29, 2017, the Company entered into a three-year software license contract with Cadence Design Systems, Inc. (“Cadence”), a related party, for the use of various Engineering Design Aid (“EDA”) software tools used for its research and development efforts. The license payments will be made and amortized over 12 quarterly periods amounting to approximately $3.3 million. In addition, the Company also contracted with Cadence for ongoing maintenance support which will be recognized ratably over the contractual term and amount to approximately $1.2 million The Company has classified these licenses as definite long-lived intangible assets in its Condensed Consolidated Balance Sheets as of October 1, 2017. Definite long-lived intangible assets consist of software licenses which are recorded based on the total contractual price. Such assets are amortized over its contractual lives and are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If it is determined that such assets are not recoverable, an impairment charge is recognized for the amount by which the carrying amount of such assets exceeds their fair values. There was no impairment of definite long-lived intangible assets for any periods presented.

The Company and Summary of Significant Accounting Policies

Quantenna Communications, Inc. (the “Company”) was incorporated in the State of Delaware on November 28, 2005. The Company designs, develops and markets advanced high-speed wireless communication solutions enabling wireless local area networking. The Company’s wireless communication solutions deliver high performance, speed, and reliability for wireless networks and devices.

Reporting Calendar

The Company prepares financial statements on a 52- or 53-week fiscal year that ends on the Sunday closest to December 31. Fiscal 2017 will have 52 weeks and fiscal 2016 had 53 weeks. In a 52-week year, each fiscal quarter consists of 13 weeks. Fiscal 2017 will end on December 31, 2017.

Initial Public Offering

On October 27, 2016, the Company’s registration statement on Form S-1 relating to its initial public offering (“IPO”) of its common stock was declared effective by the U.S. Securities and Exchange Commission (“SEC”) and the shares of its common stock began trading on the NASDAQ Global Select Market on October 28, 2016. The public offering price of the shares sold in the IPO was $16.00 per share. The IPO closed on November 2, 2016 and a second close occurred on November 25, 2016, pursuant to which the Company sold 6,775,466 shares of common stock, including the sale of 75,466 shares of common stock to the underwriters upon their exercise of their option to purchase additional shares. The Company received net proceeds of approximately $97.4 million, after underwriting discounts, commissions and offering expenses. Immediately prior to the consummation of the IPO, all outstanding shares of convertible preferred stock and preferred stock warrants were converted into common stock and common stock warrants, respectively.

Unaudited Interim Financial Information

The accompanying interim condensed consolidated financial statements and related disclosures are unaudited and in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the results of operations for the periods presented. The year-end condensed consolidated balance sheet data 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”). The condensed consolidated results of operations for the three and nine months ended October 1, 2017 are not necessarily indicative of the results to be expected for the full year or for any other future year or interim period. The accompanying condensed consolidated financial statements should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended January 1, 2017 filed with the SEC on March 1, 2017 (“2016 Annual Report on Form 10-K”).

Use of Estimates

Preparation of financial statements in conformity with US 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 reported amounts of revenue and expenses during the reporting periods covered by the financial statements and accompanying notes. Actual results could differ from those estimates.

Principles of Consolidation

The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation.

Significant Accounting Policies

During the three and nine months ended October 1, 2017, there have been no changes in our significant accounting policies as described in the Company’s 2016 Annual Report on Form 10-K, except as discussed below:

Stock-based compensation

The Company measures and recognizes compensation expense for all stock-based awards made to employees, directors and non-employees, based on estimated fair values recognized using the straight-line method over the requisite service period.

On January 1, 2017, the Company adopted the Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. Under this guidance, the Company elected the option to no longer apply a forfeiture rate to the stock-based compensation expense, but to record forfeitures when they occur, and, as a result, under the modified retrospective method of adoption the Company recorded an immaterial cumulative effect adjustment of $54,000 to the opening accumulated deficit on January 2, 2017.

Marketable Securities

Marketable securities consist primarily of highly liquid investments with maturities of greater than 90 days when purchased. We generally classify our marketable securities at the date of acquisition as available-for-sale. These securities are reported at fair value with the related unrealized gains and losses included in "Accumulated other comprehensive loss", a component of stockholders’ equity, net of tax. Any unrealized losses which are considered to be other-than-temporary impairments are recorded in "Other income (expense), net" in the Condensed Consolidated Statements of Operations. Realized gains (losses) on the sale of marketable securities are determined using the specific-identification method and recorded in "Other income (expense), net" in the Consolidated Statements of Operations.

All of our available-for-sale investments are subject to a periodic impairment review. We record a charge to earnings when a decline in fair value is significantly below cost basis and judged to be other-than-temporary, or have other indicators of impairments. If the fair value of an available-for-sale investment is less than its amortized cost basis, an other-than-temporary impairment is triggered in circumstances where (1) we intend to sell the instrument, (2) it is more likely than not that we will be required to sell the instrument before recovery of its amortized cost basis or (3) a credit loss exists where we do not expect to recover the entire amortized cost basis of the instrument. If we intend to sell or it is more likely than not that we will be required to sell the available-for-sale investment before recovery of its amortized cost basis, we recognize an other-than temporary impairment charge equal to the entire difference between the investment's amortized cost basis and its fair value.

Intangible Assets

On September 29, 2017, the Company entered into a three-year software license contract with Cadence Design Systems, Inc. (“Cadence”), a related party, for the use of various Engineering Design Aid (“EDA”) software tools used for its research and development efforts. The license payments will be made and amortized over 12 quarterly periods amounting to approximately $3.3 million. In addition, the Company also contracted with Cadence for ongoing maintenance support which will be recognized ratably over the contractual term and amount to approximately $1.2 million The Company has classified these licenses as definite long-lived intangible assets in its Condensed Consolidated Balance Sheets as of October 1, 2017.

Definite long-lived intangible assets consist of software licenses which are recorded based on the total contractual price. Such assets are amortized over its contractual lives and are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If it is determined that such assets are not recoverable, an impairment charge is recognized for the amount by which the carrying amount of such assets exceeds their fair values. There was no impairment of definite long-lived intangible assets for any periods presented.