Description of Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements include the accounts of Maxwell Technologies, Inc. and its subsidiaries and have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”). All intercompany transactions and account balances have been eliminated in consolidation. The Company has prepared the accompanying unaudited interim condensed consolidated financial statements in accordance with the instructions to Form 10-Q and the standards of accounting measurement set forth in the Interim Reporting Topic of the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”). Consequently, the Company has not necessarily included in this Form 10-Q all information and footnotes required for audited financial statements. In the opinion of the Company’s management, the accompanying unaudited condensed consolidated financial statements in this Form 10-Q contain all adjustments (consisting only of normal recurring adjustments, except as otherwise indicated) necessary to for a fair statement of the financial position, results of operations, and cash flows of Maxwell Technologies, Inc. for all periods presented. The results reported in these condensed consolidated financial statements should not be regarded as necessarily indicative of results that may be expected for any subsequent period or for the entire year. These unaudited condensed consolidated financial statements and notes thereto should be read in conjunction with the Company’s audited financial statements and the notes thereto included in the Company’s latest Annual Report on Form 10-K. Certain information and footnote disclosures normally included in the annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted in the accompanying interim consolidated financial statements. The year-end condensed balance sheet data was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP.
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 reported amounts and related disclosures. These estimates include, but are not limited to, assessing the collectability of accounts receivable, applied and unapplied production costs, production capacities, the usage and recoverability of inventories and long-lived assets, deferred income taxes, the incurrence of warranty obligations, the fair value of acquired tangible and intangible assets, impairment of goodwill and intangible assets, estimation of the cost to complete certain projects, estimation of pension assets and liabilities, estimation of employee severance benefit obligations, accruals for estimated losses for legal matters, and estimation of the value of stock-based compensation awards, including the probability that the performance criteria of restricted stock unit awards will be met.
Income Taxes	Income Taxes As of September 30, 2017, the Company has a cumulative valuation allowance recorded offsetting its worldwide net deferred tax assets of $91.0 million, of which the significant majority represents the valuation allowance on its U.S. net deferred tax asset. The Company has established a valuation allowance against its U.S. federal and state deferred tax assets due to the uncertainty surrounding the realization of such assets. Management periodically evaluates the recoverability of the deferred tax assets and at such time as it is determined that it is more likely than not that U.S. deferred tax assets are realizable, the valuation allowance will be reduced accordingly. Any such release would result in recording a tax benefit that would increase net income in the period the valuation is released. The Company records taxes on the undistributed earnings of foreign subsidiaries unless the subsidiaries’ earnings are considered indefinitely reinvested outside of the U.S. As of September 30, 2017, the Company has recorded a $4.9 million deferred tax liability for Swiss withholding taxes associated with $97.6 million of undistributed earnings of its Swiss subsidiary that are no longer considered indefinitely reinvested. In the event that the Company repatriates these funds, these withholding taxes would become payable.
Goodwill	Goodwill Goodwill, which represents the excess of the cost of an acquired business over the net fair value assigned to its assets and liabilities, is not amortized. Instead, goodwill is assessed annually at the reporting unit level for impairment under the Intangibles—Goodwill and Other Topic of the FASB ASC. The Company has established December 31 as the annual impairment test date. In addition, the Company assesses goodwill in between annual test dates if an event occurs or circumstances change that could more likely than not reduce the fair value of a reporting unit below its carrying value. The Company first makes a qualitative assessment as to whether goodwill is impaired. If it is more likely than not that goodwill is impaired, the Company performs a quantitative impairment analysis to determine if goodwill is impaired. The Company may also determine to skip the qualitative assessment in any year and move directly to the quantitative test. The quantitative goodwill impairment analysis compares the reporting unit’s carrying amount to its fair value. Goodwill impairment is recorded for any excess of a reporting unit's carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. During the year ended December 31, 2016, the Company performed a quantitative goodwill impairment analysis for one reporting unit, which required the Company to make significant assumptions and estimates about the extent and timing of future cash flows, discount rates and growth rates. The analysis indicated that the goodwill assigned to the reporting unit was not impaired.
Long-Lived Assets and Intangible Assets	Long-Lived Assets and Intangible Assets The Company records intangible assets at their respective estimated fair values at the date of acquisition. Intangible assets are amortized based upon the pattern in which their economic benefit will be realized, or if this pattern cannot be reliably determined, using the straight-line method over their estimated useful lives of eight to fourteen years. The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets, including intangible assets, may not be recoverable. When such events occur, the Company compares the carrying amounts of the assets to their undiscounted expected future cash flows. If the Company determines that the carrying value of the asset is not recoverable, a permanent impairment charge is recorded for the amount by which the carrying value of the long-lived asset exceeds its fair value.
Warranty Obligation	Warranty Obligation The Company provides warranties on all product sales for terms ranging from one to eight years. The Company accrues for the estimated warranty costs at the time of sale based on historical warranty experience plus any known or expected changes in warranty exposure.
Convertible Debt	Convertible Debt Convertible notes are regarded as compound instruments, consisting of a liability component and an equity component. The component parts of compound instruments are classified separately as financial liabilities and equity in accordance with the substance of the contractual arrangement. At the date of issue, the fair value of the liability component is estimated using the prevailing market interest rate for a similar non-convertible instrument. This amount is recorded as a liability on an amortized cost basis until extinguished upon conversion or at the instrument’s maturity date. The equity component is determined by deducting the amount of the liability component from the proceeds of the compound instrument as a whole. This is recognized as additional paid-in capital and included in equity, net of income tax effects, and is not subsequently remeasured. After initial measurement, the convertible notes are carried at amortized cost using the effective interest method.
Revenue Recognition	Revenue Recognition Revenue is derived primarily from the sale of manufactured products directly to customers. Product revenue is recognized, according to the guidelines of the Securities and Exchange Commission (“SEC”) Staff Accounting Bulletin (“SAB”) Numbers 101, Revenue Recognition in Financial Statements, and 104, Revenue Recognition, when all of the following criteria are met: (1) persuasive evidence of an arrangement exists (upon contract signing or receipt of an authorized purchase order from a customer); (2) title passes to the customer at either shipment from the Company’s facilities or receipt at the customer facility, depending on shipping terms; (3) customer payment is deemed fixed or determinable and free of contingencies or significant uncertainties; and (4) collectability is reasonably assured. This policy has been consistently applied from period to period. A portion of our revenue is derived from sales to distributors. Distributor revenue is recognized when all of the criteria for revenue recognition are met, which is generally the time of shipment to the distributor; all returns and credits are estimable and not significant. Certain distributor agreements of Nesscap Korea provide for significant rights of return and price adjustment; revenue related to these distributors is deferred until the period in which the distributor sells through the inventory to the end customer. Revenue from production-type contracts, which represents less than five percent of total revenue, is recognized using the percentage of completion method. The degree of completion is determined based on costs incurred as a percentage of total costs anticipated, excluding costs that are not representative of progress to completion. Total deferred revenue and customer deposits in the consolidated balance sheets as of September 30, 2017 and December 31, 2016 was $6.2 million and $4.0 million, respectively, and primarily relates to cash received under the localization agreement with CRRC-SRI which will be recognized over the ten-year term of the agreement, amounts received in advance from a customer in connection with a production-type contract for which revenue is recognized using the percentage of completion method, payments received under a joint development agreement, which are recognized as an offset to research and development expense as services are performed, deferred revenue for distributors on the sell-through method of recognition, and customer advances.
Net Income (Loss) per Share	Net Income (Loss) per Share In accordance with the Earnings Per Share Topic of the FASB ASC, basic net income or loss per share is calculated using the weighted average number of common shares outstanding during the period. Diluted net income per share includes the impact of additional common shares that would have been outstanding if potentially dilutive common shares were issued. Potentially dilutive securities are not considered in the calculation of diluted net loss per share, as their inclusion would be anti-dilutive.
Business Combinations	Business Combinations The Company accounts for businesses it acquires in accordance with ASC Topic 805, Business Combinations, which allocates the fair value of the purchase consideration to the tangible and intangible assets acquired and liabilities assumed based on their estimated fair values. The excess of the purchase consideration over the fair values of these identifiable assets and liabilities is recorded as goodwill. When determining the fair values of assets acquired and liabilities assumed, management makes significant estimates and assumptions. The Company may utilize third-party valuation specialists to assist the Company in the allocation. Initial purchase price allocations are subject to revision within the measurement period, not to exceed one year from the date of acquisition. Acquisition-related expenses and transaction costs associated with business combinations are expensed as incurred.
Restructuring and Exit Costs	Restructuring and Exit Costs Restructuring and exit costs involve employee-related termination costs, facility exit costs and other costs associated with restructuring activities. The Company accounts for charges resulting from operational restructuring actions in accordance with ASC Topic 420, Exit or Disposal Cost Obligations (“ASC 420”) and ASC Topic 712, Compensation-Nonretirement Postemployment Benefits (“ASC 712”). The recognition of restructuring costs requires the Company to make certain assumptions related to the amounts of employee severance benefits, the time period over which leased facilities will remain vacant and expected sublease terms and discount rates. Estimates and assumptions are based on the best information available at the time the obligation arises. These estimates are reviewed and revised as facts and circumstances dictate; changes in these estimates could have a material effect on the amount accrued in the condensed consolidated balance sheet.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers. The standard provides companies with a single model for accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. The guidance permits companies to either apply the requirements retrospectively to all prior periods presented, or apply the requirements in the year of adoption, through a cumulative adjustment. In August 2015, the FASB issued ASU 2015-14, Deferral of the Effective Date, which defers the required adoption date of ASU 2014-09 by one year. As a result of the deferred effective date, ASU 2014-09 will be effective for the Company in its first quarter of fiscal 2018. Early adoption is permitted but not before the original effective date of the new standard of the first quarter of fiscal 2017. The following ASUs were subsequently issued by the FASB to clarify the implementation guidance in some areas and add practical expedients: In March 2016, ASU 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations; in April 2016, ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing; in May 2016, ASU 2016-12, Revenue from Contracts with Customers: Narrow Scope Improvements and Practical Expedients; and in December 2016, ASU 2016-20, Technical Corrections and Improvements to Revenue from Contracts with Customers. The Company is in the process of evaluating its standard product sales arrangements and has identified an adoption impact related to revenue from certain distributor agreements which is currently deferred until the period in which the distributor sells through the inventory to the end customer. In connection with the adoption of ASU 2014-09, the Company anticipates a change in the recognition of such distributor revenue whereby revenue is estimated and recognized in the period in which the Company sells the product to the distributor; the adoption impact is expected to be less than $1.0 million. Other than this impact, the Company has not yet identified any expected material impact on the timing and measurement of revenue for standard product sales arrangements from the adoption of the standard; however, the Company is still in the process of formalizing its final conclusions. The Company is still evaluating the impact of adoption on non-product sales arrangements, which represent less than five percent of revenue. The Company has also developed a comprehensive project plan to guide implementation of the new standard and expects to complete its assessment in December 2017. The Company intends to adopt the new standard using the modified retrospective transition method effective January 1, 2018. In February 2016, the FASB issued ASU No. 2016-02, Leases. The standard requires that a lessee recognize the assets and liabilities that arise from operating leases. A lessee should recognize in its balance sheet a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize lease assets and lease liabilities. In transition, lessees and lessors are required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The guidance in ASU 2016-02 is effective for annual and interim reporting periods beginning after December 15, 2018. The Company’s initial evaluation of its current leases does not indicate that the adoption of this standard will have a material impact on its consolidated statements of operations. The Company expects that the adoption of the standard will have a material impact on its consolidated balance sheets for the recognition of certain operating leases as right-of-use assets and lease liabilities. In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting, which changes the accounting for employee share-based payments, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. Under the new guidance, excess tax benefits associated with share-based payment awards will be recognized in the income statement when the awards vest or settle, rather than in stockholders’ equity. In addition, it will increase the number of shares an employer can withhold to cover income taxes on share-based payment awards and still qualify for the exemption to liability classification. The guidance was effective for the Company in the first quarter of 2017. The adoption of this standard resulted in the recognition of approximately $10.0 million of deferred tax assets related to stock-based compensation and a corresponding increase in the Company’s valuation allowance, which will be disclosed in the Company’s notes to the consolidated financial statements in its Annual Report on Form 10-K. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows - Restricted Cash, which requires entities to show the changes in the total of cash, cash equivalents, restricted cash and restricted cash equivalents in the statement of cash flows. The guidance will be effective for the Company in its first quarter of fiscal 2018. Early adoption is permitted, including adoption in an interim period, but any adjustments must be reflected as of the beginning of the fiscal year that includes that interim period. The new standard must be adopted retrospectively. The Company early adopted this standard in the fourth quarter of 2016. In accordance with the Company’s early adoption of ASU No. 2016-18, for the nine months ended September 30, 2016, the retrospective restatement was limited to including restricted cash balances in the amount of $0.4 million in beginning and $0.1 million in ending cash, cash equivalents and restricted cash balances in the consolidated statements of cash flows. The retrospective adoption did not impact reported net loss and does not otherwise have a material impact on the presentation of the overall financial statements. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations: Clarifying the Definition of a Business, which clarifies the definition of a business and adds further guidance in evaluating whether a transaction should be accounted for as an acquisition of an asset or a business. This standard will be effective for the first annual period beginning after December 15, 2017, including interim periods within those periods. Early adoption is permitted. The Company early adopted this standard on January 1, 2017 and the adoption did not have an effect on the Company’s consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other, which eliminates step two of the quantitative goodwill impairment test. Step two required determination of the implied fair value of a reporting unit, and then a comparison of this implied fair value with the carrying amount of goodwill for the reporting unit, in order to determine any goodwill impairment. Under the new guidance, an entity is only required to complete a one-step quantitative test, by comparing the fair value of a reporting unit with its carrying amount, and any goodwill impairment charge is determined by the amount by which the carrying amount exceeds the reporting unit’s fair value. However, the loss should not exceed the total amount of goodwill allocated to the reporting unit. The standard is effective for the Company in the first quarter of 2020, with early adoption permitted as of January 1, 2017, and is to be applied on a prospective basis. The adoption of the standard will not materially impact the Company's consolidated financial statements unless step one of the annual goodwill impairment test fails. The Company early adopted this standard on January 1, 2017 and the adoption did not have an effect on the Company’s consolidated financial statements. In March 2017, the FASB issued ASU No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost, which changes how employers that sponsor defined benefit pension or other postretirement benefit plans present the net periodic benefit cost in the statement of operations. The new guidance requires entities to report the service cost component in the same line item or items as other compensation costs. The other components of net benefit cost are required to be presented in the statement of operations separately from the service cost component and outside the subtotal of loss from operations. ASU 2017-07 also provides that only the service cost component is eligible for capitalization. This standard will impact the Company’s loss from operations but will have no impact on our net loss or net loss per share. The standard is effective for the Company in the first quarter of 2018, with adoption to be applied on a retrospective basis. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation: Scope of Modification Accounting, which provides clarification on when modification accounting should be used for changes to the terms or conditions of a share-based payment award. This ASU does not change the accounting for modifications but clarifies that modification accounting guidance should only be applied if there is a change to the value, vesting conditions or award classification and would not be required if the changes are considered non-substantive. The amendments of this ASU are effective for the Company in the first quarter of 2018, with early adoption permitted. The adoption of ASU 2017-09 is not expected to have an impact on the Company’s consolidated financial statements. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging - Targeted Improvements to Accounting for Hedging Activities, which modifies the presentation and disclosure of hedging results. Further, it provides partial relief on the timing of certain aspects of hedge documentation and eliminates the requirement to recognize hedge ineffectiveness separately in income. The amendments in this ASU are effective for the Company in the first quarter of 2019. The Company does not expect this ASU to have a material impact on its consolidated financial statements. There have been no other recent accounting standards, or changes in accounting standards, during the nine months ended September 30, 2017, as compared with the recent accounting standards described in our Annual Report on Form 10-K, that are of material significance, or have potential material significance, to the Company.
Fair Value Measurements	The Company records certain financial instruments at fair value in accordance with the Fair Value Measurements and Disclosures Topic of the FASB ASC. Historically, the financial instruments to which this topic applied were foreign currency forward contracts and the fair value of these foreign currency forward contracts was recorded as a liability or asset in the consolidated balance sheets. During the second quarter of 2016, the Company ceased using foreign currency forward contracts to hedge foreign currency exposure as management determined its foreign currency exposure was no longer sufficiently significant to merit the use of hedging instruments. Therefore, no foreign currency forward contracts were outstanding as of September 30, 2017. The fair value of these derivative instruments was measured using models following quoted market prices in active markets for identical instruments, which is a Level 2 input under the fair value hierarchy of the Fair Value Measurements and Disclosures Topic of the FASB ASC.
Foreign Currency Derivative Instruments	The Company has historically used forward contracts to hedge certain monetary assets and liabilities, primarily receivables, payables and cash balances, denominated in foreign currencies. During the second quarter of 2016, the Company ceased using foreign currency forward contracts to hedge foreign currency exposure as management determined its foreign currency exposure was no longer sufficiently significant to merit the use of hedging instruments. The change in fair value of these forward contracts represented a natural hedge as gains and losses on these instruments partially offset the changes in the fair value of the underlying monetary assets and liabilities due to movements in currency exchange rates. These forward contracts generally expired in one month. These contracts were considered economic hedges but were not designated as hedges under the Derivatives and Hedging Topic of the FASB ASC, therefore, the change in the fair value of the instrument was recognized each period in the consolidated statement of operations.
Maxwell SA Pension Plan	Maxwell SA has a retirement plan that is classified as a defined benefit pension plan. The employee pension benefit is based on compensation, length of service and credited investment earnings. The plan guarantees both a minimum rate of return as well as minimum annuity purchase rates. The Company’s funding policy with respect to the pension plan is to contribute the amount required by Swiss law, using the required percentage applied to the employee’s compensation. In addition, participating employees are required to contribute to the pension plan. This plan has a measurement date of December 31.