Description of Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2019
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 or 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 income (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 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. The Company adopted the new accounting standard using the modified retrospective transition option effective January 1, 2019. In connection with the adoption of this standard, on January 1, 2019, the Company recorded $9.1 million of right-of-use assets and $11.6 million of lease liabilities on its consolidated balance sheet for the recognition of operating leases as right-of-use assets and lease liabilities. The adoption of this standard did not have a material impact on the Company’s consolidated statements of operations. See further information in Note 4. In August 2018, the FASB issued ASU No. 2018-14, Compensation - Retirement Benefits - Defined Benefit Plans - General. This ASU modifies the disclosure requirements for defined benefit and other postretirement plans. This ASU eliminates certain disclosures associated with accumulated other comprehensive income, plan assets, related parties, and the effects of interest rate basis point changes on assumed health care costs; while other disclosures have been added to address significant gains and losses related to changes in benefit obligations. This ASU also clarifies disclosure requirements for projected benefit and accumulated benefit obligations. The amendments in this ASU are effective for fiscal years ending after December 15, 2020 and for interim periods therein with early adoption permitted. Adoption on a retrospective basis for all periods presented is required. The Company is currently evaluating the impact of adoption on its financial statement disclosures. There have been no other recent accounting standards, or changes in accounting standards, during the three months ended March 31, 2019, 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	The Company’s revenues primarily result from the sale of manufactured products and reflect the consideration to which the Company expects to be entitled. The Company records revenue based on a five-step model in accordance with ASC 606. For its customer contracts, the Company identifies the performance obligations, determines the transaction price, allocates the contract transaction price to the performance obligations, and recognizes the revenue when (or as) control of goods or services is transferred to the customer. For product sales, each purchase order, along with any existing governing customer agreements where applicable, represents a contract with a customer and each product sold to a customer typically represents a distinct performance obligation. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. The majority of the Company’s product sales are subject to ExWorks delivery terms (as defined in Incoterms 2010) and revenue is recorded at the point in time when products are picked up by the customer's freight forwarder, as the Company has determined that this is the point in time that control transfers to the customer. Certain customers have shipping terms where control does not transfer until the product is delivered to the customer’s location. For these transactions, revenue is recognized at the time that the product is delivered to the customer’s location. Provisions for customer volume discounts, product returns, rebates and allowances are variable consideration and are estimated and recorded as a reduction of revenue in the same period the related product revenue is recorded. Such provisions are calculated using historical averages and adjusted for any expected changes due to current business conditions, and are not material. The Company provides assurance-type 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. The Company records revenue net of sales tax, value added tax, excise tax and other taxes collected concurrent with revenue-producing activities. The Company has elected to recognize the cost for freight and shipping when control over the products sold passes to customers and revenue is recognized. The Company’s contracts with customers do not typically include extended payment terms. Payment terms vary by contract type and type of customer and generally range from 30 to 90 days from delivery. A portion of the Company’s revenue is derived from sales to distributors which represented approximately 13% and 10% of revenue for the three months ended March 31, 2019 and 2018, respectively. The Company also derives some revenue from non-product sales. When the Company’s contracts with customers require specialized services or other deliverables that are not separately identifiable from other promises in the contracts and, therefore, not distinct, then the non-distinct obligations are accounted for as a single performance obligation. For performance obligations that the Company satisfies over time, which represented 2% and 6% of revenue for the three months ended March 31, 2019 and 2018, respectively, revenue is recognized by consistently applying a method of measuring progress toward complete satisfaction of that performance obligation. The Company uses the input method to recognize revenue on the basis of the Company’s efforts or inputs to the satisfaction of a performance obligation relative to the total inputs expected to satisfy that performance obligation. The Company uses the actual costs incurred relative to the total estimated costs to determine its progress towards contract completion.
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	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.
Defined Benefit Plan	Korea Defined Benefit Plan In connection with our acquisition of Maxwell Korea, the Company assumed the defined benefit plan liability related to employees of Maxwell Korea. Pursuant to the Labor Standards Act of Korea, employees and most executive officers with one or more years of service are entitled to lump sum separation benefits upon the termination of their employment based on their length of service and rate of pay.