Significant Accounting Policies (Policies)	12 Months Ended
Significant Accounting Policies (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Principles of consolidation	Principles of consolidation — The Consolidated Financial Statements include the accounts of Lydall, Inc. and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated.
Estimates and assumptions	Estimates and assumptions — The preparation of the Company’s Consolidated Financial Statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the financial statement dates and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates.
Risks and uncertainties	Risks and uncertainties — Worldwide economic cycles and political changes affect the markets that the Company’s businesses serve and affect demand for Lydall’s products and impact profitability. Among other factors, disruptions in the global credit and financial markets, including diminished liquidity and credit availability, swings in consumer confidence and spending, unstable economic growth and fluctuations in unemployment rates has caused economic instability and can have a negative impact on the Company’s results of operations, financial condition and liquidity.
Cash and cash equivalents	Cash and cash equivalents — Cash and cash equivalents include cash on hand and highly liquid investments with original maturities of three months or less at the date of purchase.
Concentration of credit risk	Concentrations of credit risk — Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and trade accounts receivable. The Company places its cash and cash equivalents in high-quality financial institutions. Concentrations of credit risk with respect to trade accounts receivable are limited by the large number of customers comprising the Company’s customer base and their dispersion across many different industries and geographies.
Inventories	Inventories — Inventories are valued at lower of cost or net realizable value, cost being determined using the first-in, first-out (FIFO) cost method. Inventories in excess of requirements for current or anticipated orders have been written down to net realizable value.
Pre-production design and development costs	Pre-production design and development costs — The Company enters into contractual agreements with certain customers to design and develop molds, dies and tools (collectively, “tooling”). All such tooling contracts relate to parts that the Company will supply to customers under long-term supply agreements. Tooling costs are accumulated in work-in process inventory and are charged to operations as the related revenue from the tooling is recognized. Revenue is recognized as tooling is delivered and accepted by the customer. The Company also may progress bill on certain tooling being constructed. These billings are recorded as progress billings (a reduction of the associated work-in-process inventory) until the appropriate revenue recognition criteria have been met. Periodically, the Company enters into contractually guaranteed reimbursement arrangements as a mechanism to collect amounts due from customers from tooling sales. Under these arrangements, amounts due from tooling sales are collected as parts are delivered over the part supply arrangement, in accordance with the specific terms of the arrangement. The amounts due from the customer in such transactions are recorded in “Prepaid expenses and other current assets” or “Other assets, net” based upon the expected term of the reimbursement arrangement.
Property, plant and equipment	Property, plant and equipment — Property, plant, and equipment are stated at cost. Assets held under capital leases are recorded at the lower of the net present value of the minimum lease payments or the fair value of the leased asset at the inception of the lease. Property, plant and equipment, including property, plant and equipment under capital leases, are depreciated over their estimated useful lives using the straight-line method. Leasehold improvements are depreciated on a straight-line basis over the term of the lease or the life of the asset, whichever is shorter. The cost and accumulated depreciation amounts applicable to assets sold or otherwise disposed of are removed from the asset and accumulated depreciation accounts and any net gain or loss is included in the Consolidated Statements of Operations. Expenses for maintenance and repairs are charged to expense as incurred.
Goodwill and other intangible assets	Goodwill and other intangible assets — Goodwill represents costs in excess of fair values assigned to the underlying net assets of acquired companies. Goodwill and other intangible assets with indefinite lives are not amortized but are subject to annual impairment tests. All other intangible assets are amortized over their estimated useful lives, which range from 4 to 14 years. In performing impairment tests, the Company considers discounted cash flows and other market factors as best evidence of fair value. There are inherent uncertainties and management judgment required in these analyses.
Valuation of long-lived assets	Valuation of long-lived assets — The Company evaluates the recoverability of long-lived assets, or asset groups, whenever events or changes in circumstances indicate that carrying amounts may not be recoverable. Should such evaluations indicate that the related future undiscounted cash flows are not sufficient to recover the carrying values of the assets, such carrying values would be reduced to fair value and this adjusted carrying value would become the assets’ new cost basis. For long-lived assets held for sale, assets are written down to fair value, less costs to sell. Fair value is determined primarily using future anticipated cash flows that are directly associated with, and that are expected to arise as a direct result of the use and eventual disposition of the asset, or asset group, as well as market conditions and other factors. There are inherent uncertainties and management judgment required in these analyses.
Contingencies and environmental obligations	Contingencies and environmental obligations — The Company makes judgments and estimates in accordance with applicable accounting rules when it establishes reserves for legal proceedings, claims, investigations, environmental obligations and other contingent matters. Provisions for such matters are charged to expense when it is probable that a liability has been incurred and reasonable estimates of the liability can be made. Estimates of environmental liabilities are based on a variety of matters, including, but not limited to, the stage of investigation, the stage of the remedial design, evaluation of existing remediation technologies, and presently enacted laws and regulations. The amount and timing of all future expenses related to legal proceedings, claims, investigations, environmental obligations and other contingent matters may vary significantly from estimates.
Employer sponsored benefit plans	Employer sponsored benefit plans — The Company recognizes the funded status of its domestic defined benefit pension plan. Net benefit obligations are calculated based on actuarial valuations using key assumptions related to discount rates, mortality rates and expected return on plan assets.
Derivative instruments	Derivative instruments — Derivative instruments are measured at fair value and recognized as either assets or liabilities on the Consolidated Balance Sheet in either current or non-current other assets or other accrued liabilities or other long-term liabilities depending upon maturity and commitment. For derivative instruments that are designated and qualify as a fair value hedge, the gain or loss on the derivative as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in the Consolidated Statement of Operations. For derivative instruments that are designated and qualify as a cash flow hedge, the effective portion of the gain or loss on the derivative is reported as a component of other comprehensive income and reclassified into earnings in the same period or periods in which the hedge transaction affects earnings. The Company selectively uses financial instruments to manage market risk associated with exposure to fluctuations in interest rates and foreign currency rates. These financial exposures are monitored and managed by the Company as an integral part of its risk management program. The Company does not engage in derivative instruments for speculative or trading purposes. Lydall has historically not been a party to a significant number of derivative instruments. Derivatives The Company selectively uses financial instruments to manage market risk associated with exposure to fluctuations in interest rates and foreign currency rates. These financial exposures are monitored and managed by the Company as an integral part of its risk management program. The Company’s interest rate exposure is most sensitive to fluctuations in interest rates in the United States and Europe, which impact interest paid on its debt. The Company has debt with variable rates of interest based generally on LIBOR. From time to time, the Company may enter into interest rate swap agreements to manage interest rate risk. These instruments are designated as cash flow hedges and are recorded at fair value using Level 2 observable market inputs. Derivative instruments are recognized as either assets or liabilities on the balance sheet in either current or non-current other assets or other accrued liabilities or other long-term liabilities depending upon maturity and commitment. For derivative instruments that are designated and qualify as a cash flow hedge, the effective portion of the gain or loss on the derivative is reported as a component of other comprehensive income and reclassified into earnings in the same period or periods in which the hedge transaction affects earnings. Any ineffective portion, or amounts related to contracts that are not designated as hedges, are recorded directly to earnings. The Company's policy for classifying cash flows from derivatives is to report the cash flows consistent with the underlying hedged item. The Company does not use derivatives for speculative or trading purposes.
Revenue recognition	Revenue recognition — The Company recognizes revenue (1) once evidence of an arrangement exists; (2) product delivery has occurred; (3) pricing is fixed or determinable; and (4) collection is reasonably assured. The four criteria required to recognize revenue are considered to be met, and the passage of title to the customer occurs, at the respective FOB point and, therefore, revenue is recognized at that time. The Company’s standard sales and shipping terms are FOB shipping point, therefore, substantially all revenue is recognized upon shipment. However, the Company conducts business with certain customers on FOB destination terms and in these instances revenue is recognized upon receipt by the customer. The Company generally does not provide specific customer inspection or acceptance provisions in its sales terms, with the exception of tooling sales discussed in “Pre-production design and development costs” above. Sales returns and allowances are recorded as identified or communicated by the customer and internally approved. The Company does not provide customers with general rights of return for products sold; however, in limited circumstances, the Company will allow sales returns and allowances from customers if the products sold do not conform to specifications. Shipping and handling costs consist primarily of costs incurred to deliver products to customers and internal costs related to preparing products for shipment and are recorded in cost of sales. Amounts billed to customers as shipping and handling are classified as revenue.
Research and development	Research and development — Research and development costs are charged to expense as incurred and amounted to $10.8 million in 2017, $9.0 million in 2016, and $8.5 million in 2015. Research and development costs were primarily comprised of development personnel salaries, prototype material costs and testing and trials of new products.
Earnings per share	Earnings per share — Basic earnings per common share are equal to net income divided by the weighted average number of common shares outstanding during the period. Diluted earnings per common share are equal to net income divided by the weighted average number of common shares outstanding during the period, including the effect of stock options and stock awards, if such effect is dilutive.
Income taxes	Income taxes — The provision for income taxes is based upon income reported in the accompanying Consolidated Financial Statements. Deferred income taxes reflect the impact of temporary differences between the amounts of income and expense recognized for financial reporting purposes and such amounts recognized for tax purposes. In the event the Company was to determine that it would not be able to realize all or a portion of its deferred tax assets in the future, the Company would record a valuation allowance through a charge to income in the period that such determination was made. Conversely, if the Company was to determine that it would be able to realize its deferred tax assets in the future in excess of the net carrying amounts, the Company would decrease the recorded valuation allowance and record an increase to income in the period that such determination was made.
Translation of foreign currencies	Translation of foreign currencies — Assets and liabilities of foreign subsidiaries are translated at exchange rates prevailing on the balance sheet date. Revenues and expenses are translated at average exchange rates prevailing during the period. Any resulting translation gains or losses are reported in other comprehensive income (loss).
Stock options and share grants	Stock options and share grants — The Company accounts for awards of equity instruments under the fair value method of accounting and recognizes such amounts in the Consolidated Statements of Operations. The Company recognizes expense on a straight-line basis over the vesting period of the entire award. Prior to January 1, 2016, stock-based compensation expense included estimated effects of forfeitures. Upon adoption of ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, in 2016, an accounting policy election was made to account for forfeitures as they occur. As a result of the adoption of this ASU, the Company recognized excess tax benefits from stock award exercises and vesting as a discrete tax benefit during the years ended December 31, 2017 and December 31, 2016. The Company applied these changes prospectively, and therefore the year ending December 31, 2015 was not adjusted. The Company estimates the fair value of option grants based on the Black Scholes option-pricing model. Expected volatility and expected term are based on historical information. The calculation assumes that future volatility and expected term are not likely to materially differ from the Company’s historical stock price volatility and historical exercise data, respectively. Compensation expense for all restricted stock awards is recorded based on the market value of the stock on the grant date and recognized as expense over the vesting period of the award. Compensation expense for performance-based restricted stock is also impacted by the probability of achieving the performance targets.
Recently adopted accounting standards and recently issued accounting standards	Recently Adopted Accounting Standards Effective January 1, 2017, the Company adopted the Financial Accounting Standards Board ("FASB") Accounting Standards Update ("ASU") No. 2015-11, “Inventory” (Topic 330): Simplifying the Measurement of Inventory." This ASU requires an entity to measure inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. Subsequent measurement is unchanged for inventory measured using last-in, first-out (“LIFO”) or the retail inventory method. The adoption of this ASU did not have any impact on the Company’s consolidated financial statements. Recently Issued Accounting Standards In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)." The objective of this standard update is to remove inconsistent practices with regard to revenue recognition between US GAAP and IFRS. The standard intends to improve comparability of revenue recognition practices across entities, industries, jurisdictions and capital markets. ASU 2014-09 is effective for the Company’s interim and annual reporting periods beginning January 1, 2018, and is to be adopted using either a full retrospective or modified retrospective transition method with early adoption permitted for annual periods beginning after December 15, 2016. The new standard requires new comprehensive qualitative and quantitative disclosures relating to the nature, amount, timing and uncertainty of revenue arising from contracts with customers, including significant judgments and estimates used when applying the guidance. Subsequent to the issuance of ASU No. 2014-09, the FASB has issued the following update; ASU No. 2016-20, “Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers”. The amendments in this update affects the guidance contained within ASU 2014-09 and were assessed as part of the Company's revenue recognition project plan. In the first quarter of 2018, the Company will complete its conversion activities, including the integration of the standard update into financial reporting processes and systems, and the final cumulative effect adjustment to be recorded upon implementation of ASU 2014-09. The Company continues to assess the impacts to all of its segments under the new standard and has identified an impact to the timing of revenue recognition across all segments. The Company currently recognizes revenue at a point in time typically when products are shipped and risk of loss has transferred to the customer, whereas the implementation of the new standard will result in revenue associated with certain customer contracts moving to an over-time revenue recognition model. Under the new standard, the customized nature of some products combined with contractual provisions that provide the Company with an enforceable right to payment will require the Company to recognize revenue related to these customer contracts prior to the product being shipped to the customer. As such, revenue associated with these contracts will be recognized as costs are incurred. This change generally results in an acceleration of revenue compared with the Company's previous revenue recognition method for these contracts. The Company will adopt ASU 2014-09 effective January 1, 2018, under the modified retrospective transition method. At the adoption date, the cumulative impact of revenue that would have been recognized over time, is expected to be approximately $17.0 million to $23.0 million. The impact is primarily driven by tooling net sales of approximately $15.0 million to $19.0 million from customer contracts within the TAS segment. The Company expects the related adoption impact to retained earnings to be approximately $1.0 million to $2.5 million, primarily due to lower margin tooling net sales and will recognize the cumulative effect of these adjustments net of tax. Additionally, the Company will recognize the cumulative effect of adoption on its Consolidated Balance sheet primarily as an increase in unbilled accounts receivable and a reduction in inventoriable costs as of January 1, 2018. The Company is also evaluating the disclosure requirements under the new standard that are effective in the first quarter of 2018, including disclosure of contract assets as well as disaggregated presentation of revenue. The new standard also requires expanded disclosure regarding the nature, timing, and uncertainty of revenue, cash flow and customer contract balances, including how and when the Company satisfies its performance obligations and the relationship between revenue recognized and changes in contract balances during a reporting period. The Company will continue to evaluate these disclosure requirements and incorporated the collection of relevant data into its reporting process in the first quarter of 2018. During the first quarter of 2018, the Company will continue to analyze the adoption impact and disclose the final impact in the March 31, 2018 Form 10-Q. In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2016-02, "Leases (Topic 842)". This ASU requires entities that lease assets with lease terms of more than 12 months to recognize right-of-use assets and lease liabilities created by those leases on their balance sheets. The ASU will also require new qualitative and quantitative disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. This ASU is effective for fiscal years beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the method and impact the adoption of ASU 2016-02 will have on the Company’s consolidated financial statements and disclosures. In January 2017, the FASB issued ASU 2017-01, "Business Combinations (Topic 805): Clarifying the Definition of a Business", which adds guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. The a mendments of this ASU provide a screen to determine when an integrated set of assets and activities is not a business. The ASU is effective for fiscal years beginning after December 15, 2017. The Company is currently evaluating the impact the adoption of ASU 2017-01 will have on the Company’s consolidated financial statements and disclosures. In January 2017, the FASB issued ASU 2017-04, "Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment", which eliminates Step 2 from the goodwill impairment test. Instead, an entity should perform its annual or interim goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The ASU is effective for fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently evaluating the impact the adoption of ASU 2017-04 will have on the Company’s consolidated financial statements and disclosures. In May 2017, the FASB issued ASU No. 2017-09, "Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting". This ASU requires an entity to apply modification accounting in Topic 718 when there are changes to the terms or conditions of a share-based payment award, unless the fair value, vesting conditions, and classification of the modified award are the same as the original award immediately before the original award is modified. This ASU is effective for fiscal years beginning after December 15, 2017, with early adoption permitted. The Company is currently evaluating the method and impact the adoption of ASU 2017-09 will have on the Company’s consolidated financial statements and disclosures. In August 2017, the FASB issued ASU No. 2017-12, "Derivatives and Hedging (Topic 815): Targeted Improvements to Account for Hedging Activities". This ASU provides various improvements revolving around the financial reporting of hedging relationships that will require an entity to amend the presentation and disclosure of hedging activities to better portray the economic results of an entity's risk management activities in its financial statements. This ASU will also require an entity with cash flow and net investment hedges existing at the date of the adoption to apply a cumulative-effect adjustment related to eliminating the separate measurement of ineffectiveness to accumulated other comprehensive income with a corresponding adjustment to the opening balance of retained earnings as of the beginning of the fiscal year that the entity adopts this ASU. This ASU is effective for fiscal years beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the method and impact the adoption of ASU 2017-12 will have on the Company’s consolidated financial statements and disclosures. In February 2018, the FASB issued ASU No. 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income". This ASU allows for reclassification of stranded tax effects resulting from the Tax Cuts and Jobs Act from accumulated other comprehensive income to retained earnings. This ASU is effective for fiscal years beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the method and impact the adoption of ASU 2018-02 will have on the Company’s consolidated financial statements and disclosures.