Description of Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2018
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; estimates of returns, rebates, discounts and allowances in the recognition of revenue; estimated 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.
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.
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.
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. ASU 2014-09 and its related amendments provide companies with a single model for accounting for revenue arising from contracts with customers and supersedes prior 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. The Company adopted the new accounting standard using the modified retrospective transition method effective January 1, 2018 and recorded a $0.3 million impact to “accumulated deficit” in the Company’s consolidated balance sheet. See Note 2 for further information. 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 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 impacts the Company’s gross profit and loss from operations but has no impact on net loss or net loss per share. The Company adopted ASU 2017-07 on January 1, 2018, with adoption applied on a retrospective basis. The Company used the practical expedient that permits it to use the amounts previously disclosed in the defined benefit plans note for the prior comparative periods as the basis for applying the retrospective presentation requirements. In connection with this adoption, the Company reclassified $83,000, $52,000 and $20,000 of net non-service costs and income from cost of revenue, selling, general and administrative expense and research and development expense, respectively to “defined benefit plan income, net” for the three months ended March 31, 2017. In February 2018, the FASB issued ASU No. 2018-02, Income Statement-Reporting Comprehensive Income, which amends the previous guidance to allow for certain tax effects “stranded” in accumulated other comprehensive income, which are impacted by the Tax Cuts and Jobs Act, to be reclassified from accumulated other comprehensive income into retained earnings. This amendment pertains only to those items impacted by the new tax law and will not apply to any future tax effects stranded in accumulated other comprehensive income. This standard is effective for the Company in the first quarter of 2019, with early adoption permitted. The Company does not expect this ASU to have a material impact on its consolidated financial statements. In March 2018, the FASB issued ASU No. 2018-05, Income Taxes: Amendments to SEC paragraphs pursuant to SEC Staff Accounting Bulletin No. 118. The Amendments in this update add various SEC paragraphs pursuant to the issuance of SEC Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“SAB 118”). SAB 118 directs taxpayers to consider the implications of the Tax Cuts and Jobs Act as provisional when it does not have the necessary information available, prepared, or analyzed in reasonable detail to complete its accounting for the change in the tax law. The Company recognized the provisional tax impacts of the Tax Cuts and Jobs Act in the fourth quarter of 2017, therefore, the Company’s subsequent adoption of ASU 2018-05 in the first quarter of 2018 had no impact on its accounting for income taxes. There have been no other recent accounting standards, or changes in accounting standards, during the three months ended March 31, 2018, 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.
Revenue Recognition	On January 1, 2018, The Company adopted ASC 606, Revenue from Contracts with Customers and all the related amendments and applied it to all contracts that were not completed as of January 1, 2018 using the modified retrospective method. The Company recognized the cumulative effect of initially applying the new revenue standard as an adjustment to the opening balance of accumulated deficit. Prior period amounts have not been restated and continue to be reported under the accounting standards in effect for those periods. The Company’s adoption impact related to the recognition of certain previously deferred distributor revenue. The Company does not expect a material impact to its consolidated statements of operations on an ongoing basis from the adoption of the new standard.
Fair Value Measurements	The Company records certain financial instruments at fair value in accordance with the hierarchy from the Fair Value Measurements and Disclosures Topic of the FASB ASC as follows. Fair Value of Assets Level 1: Observable inputs such as quoted prices in active markets for identical assets. Level 2: Inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3: Unobservable inputs that reflect the reporting entity’s own assumptions.
Income Taxes	On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act. The legislation significantly changes U.S. tax law by, among other things, reducing the US federal corporate tax rate from 35% to 21%, implementing a territorial tax system and imposing a repatriation tax on deemed repatriated earnings of foreign subsidiaries. Pursuant to ASU No. 2018-05, given the amount and complexity of the changes in the tax law resulting from the tax legislation, the Company has not finalized the accounting for the income tax effects of the tax legislation. This includes the provisional amounts recorded related to the transition tax and the remeasurement of deferred taxes. The impact of the tax legislation may differ from this estimate, during the one-year measurement period due to, among other things, further refinement of the Company’s calculations, changes in interpretations and assumptions the Company has made, guidance that may be issued and actions the Company may take as a result of the tax legislation.
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.