$LFUS
LITTELFUSE INC /DE Stock $lfus

$lfus Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-K Financial Statement

#000088933121000010 Filed on February 18, 2021

Income Statement

Concept	2019 Q4	2019 Q3	2019 Q2
Revenue	$338.5M	$362.0M	$397.9M
YoY Change	-15.85%	-17.58%	-13.35%
Cost Of Revenue	$220.2M	$231.0M	$256.1M
YoY Change	-10.89%	-11.01%	-11.76%
Gross Profit	$113.7M	$132.7M	$144.3M
YoY Change	-26.31%	-26.11%	-14.6%
Gross Profit Margin	33.6%	36.66%	36.27%
Selling, General & Admin	$45.60M	$54.22M	$57.67M
YoY Change	-18.28%	-22.3%	-21.27%
% of Gross Profit	40.09%	40.86%	39.96%
Research & Development	$17.40M	$19.73M	$21.46M
YoY Change	-19.07%	-3.55%	-5.67%
% of Gross Profit	15.3%	14.87%	14.87%
Depreciation & Amortization	$23.40M	$23.09M	$22.69M
YoY Change	-13.65%	-12.07%	-13.37%
% of Gross Profit	20.57%	17.4%	15.72%
Operating Expenses	$83.90M	$83.78M	$89.17M
YoY Change	-17.99%	-18.95%	-18.46%
Operating Profit	$32.32M	$47.17M	$52.63M
YoY Change	-37.4%	-38.12%	-11.72%
Interest Expense	-$5.000M	$5.559M	$5.589M
YoY Change	-54.95%	-3.74%	-3.34%
% of Operating Profit	-15.47%	11.79%	10.62%
Other Income/Expense, Net	-$2.800M	$4.764M	$2.947M
YoY Change	250.0%	-478.4%	75.63%
Pretax Income	$24.50M	$41.40M	$53.57M
YoY Change	-38.44%	-39.3%	2.39%
Income Tax	$1.800M	$5.757M	$9.775M
% Of Pretax Income	7.35%	13.9%	18.25%
Net Earnings	$22.65M	$35.65M	$43.79M
YoY Change	-30.65%	-33.43%	3.46%
Net Earnings / Revenue	6.69%	9.85%	11.01%
Basic Earnings Per Share	$0.93	$1.46	$1.77
Diluted Earnings Per Share	$0.92	$1.44	$1.75
COMMON SHARES
Basic Shares Outstanding	24.36M shares	24.48M shares	24.74M shares
Diluted Shares Outstanding		24.68M shares	24.98M shares

Balance Sheet

Concept	2019 Q4	2019 Q3	2019 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments	$531.2M	$476.1M	$474.8M
YoY Change	8.45%	-4.46%	16.32%
Cash & Equivalents	$531.1M	$476.1M	$474.8M
Short-Term Investments	$0.00	$0.00	$0.00
Other Short-Term Assets	$28.60M	$62.40M	$63.30M
YoY Change	-41.99%	28.13%	38.51%
Inventory	$237.5M	$240.1M	$254.3M
Prepaid Expenses
Receivables	$202.3M	$226.4M	$245.7M
Other Receivables	$4.800M	$2.700M	$1.400M
Total Short-Term Assets	$1.004B	$1.008B	$1.040B
YoY Change	-2.72%	-4.28%	8.49%
LONG-TERM ASSETS
Property, Plant & Equipment	$344.6M	$329.8M	$338.5M
YoY Change	1.39%	-4.1%	-0.08%
Goodwill	$820.6M	$813.7M	$826.4M
YoY Change	-0.74%	-2.01%	-0.7%
Intangibles	$321.2M	$326.4M	$341.2M
YoY Change	-11.13%	-13.45%	-12.53%
Long-Term Investments	$11.10M	$26.70M	$25.50M
YoY Change	-4.31%	-8.25%	-18.53%
Other Assets	$14.97M	$18.16M	$18.02M
YoY Change	-28.64%	-15.13%	-33.54%
Total Long-Term Assets	$1.556B	$1.544B	$1.582B
YoY Change	-1.66%	-4.16%	-2.93%
TOTAL ASSETS
Total Short-Term Assets	$1.004B	$1.008B	$1.040B
Total Long-Term Assets	$1.556B	$1.544B	$1.582B
Total Assets	$2.560B	$2.551B	$2.622B
YoY Change	-2.08%	-4.21%	1.3%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$117.3M	$107.2M	$123.1M
YoY Change	-7.13%	-17.45%	-3.32%
Accrued Expenses	$84.12M	$114.5M	$111.7M
YoY Change	-39.22%	54.62%	68.37%
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due	$10.00M	$10.00M	$10.00M
YoY Change	0.0%	-0.75%	-0.6%
Total Short-Term Liabilities	$225.6M	$248.7M	$266.4M
YoY Change	-23.61%	-18.14%	-0.28%
LONG-TERM LIABILITIES
Long-Term Debt	$669.2M	$668.2M	$676.9M
YoY Change	-2.27%	-3.25%	-1.54%
Other Long-Term Liabilities	$64.04M	$64.50M	$65.94M
YoY Change	-11.35%	-4.31%	-13.31%
Total Long-Term Liabilities	$733.2M	$732.7M	$742.9M
YoY Change	-3.14%	-3.35%	-2.71%
TOTAL LIABILITIES
Total Short-Term Liabilities	$225.6M	$248.7M	$266.4M
Total Long-Term Liabilities	$733.2M	$732.7M	$742.9M
Total Liabilities	$958.8M	$981.4M	$1.009B
YoY Change	-8.88%	-7.58%	-2.08%
SHAREHOLDERS EQUITY
Retained Earnings	$950.9M	$939.9M	$916.0M
YoY Change	11.02%	12.63%	15.68%
Common Stock	$256.0K	$256.0K	$255.0K
YoY Change	0.79%	0.79%	0.79%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$216.4M	$216.4M	$166.1M
YoY Change	85.86%	345.73%	243.57%
Treasury Stock Shares	1.474M shares	1.474M shares	1.157M shares
Shareholders Equity	$1.496B	$1.472B	$1.510B
YoY Change
Total Liabilities & Shareholders Equity	$2.560B	$2.551B	$2.622B
YoY Change	-2.08%	-4.21%	1.3%

Cashflow Statement

Concept	2019 Q4	2019 Q3	2019 Q2
OPERATING ACTIVITIES
Net Income	$22.65M	$35.65M	$43.79M
YoY Change	-30.65%	-33.43%	3.46%
Depreciation, Depletion And Amortization	$23.40M	$23.09M	$22.69M
YoY Change	-13.65%	-12.07%	-13.37%
Cash From Operating Activities	$84.40M	$80.80M	$49.20M
YoY Change	5.9%	-27.34%	-31.28%
INVESTING ACTIVITIES
Capital Expenditures	-$23.50M	-$13.20M	-$11.10M
YoY Change	24.34%	-15.38%	-50.45%
Acquisitions
YoY Change
Other Investing Activities	$0.00	$0.00	$5.600M
YoY Change	-100.0%	-100.0%	-243.59%
Cash From Investing Activities	-$23.50M	-$13.20M	-$5.600M
YoY Change	72.79%	-26.26%	-78.71%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-10.80M	-59.90M	-44.30M
YoY Change	-85.29%	6555.56%	0.45%
NET CHANGE
Cash From Operating Activities	84.40M	80.80M	49.20M
Cash From Investing Activities	-23.50M	-13.20M	-5.600M
Cash From Financing Activities	-10.80M	-59.90M	-44.30M
Net Change In Cash	50.10M	7.700M	-700.0K
YoY Change	-786.3%	-91.67%	-158.33%
FREE CASH FLOW
Cash From Operating Activities	$84.40M	$80.80M	$49.20M
Capital Expenditures	-$23.50M	-$13.20M	-$11.10M
Free Cash Flow	$107.9M	$94.00M	$60.30M
YoY Change	9.43%	-25.87%	-35.85%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2020	dei	Entity Central Index Key EntityCentralIndexKey	0000889331
CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Entity Registrant Name EntityRegistrantName	LITTELFUSE INC /DE
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2020	dei	Amendment Flag AmendmentFlag	false
CY2020Q4	us-gaap	Operating Lease Liability Current Statement Of Financial Position Extensible List OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList	us-gaap:AccruedLiabilitiesCurrent
CY2019Q4	us-gaap	Operating Lease Liability Current Statement Of Financial Position Extensible List OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList	us-gaap:AccruedLiabilitiesCurrent
CY2020	dei	Document Type DocumentType	10-K
CY2020	dei	Document Annual Report DocumentAnnualReport	true
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-26
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-26
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	0-20388
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Chicago
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	IL
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	36-3795742
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	8755 West Higgins Road
CY2020	dei	Entity Address Address Line2 EntityAddressAddressLine2	Suite 500
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	60631
CY2020	dei	City Area Code CityAreaCode	773
CY2020	dei	Local Phone Number LocalPhoneNumber	628-1000
CY2020	dei	Security12b Title Security12bTitle	Common Stock, $0.01 par value
CY2020	dei	Trading Symbol TradingSymbol	LFUS
CY2020	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2020	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2020	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2020	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2020	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2020	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2020	dei	Entity Small Business EntitySmallBusiness	false
CY2020	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2020	dei	Icfr Auditor Attestation Flag IcfrAuditorAttestationFlag	true
CY2020	dei	Entity Shell Company EntityShellCompany	false
CY2020Q2	dei	Entity Public Float EntityPublicFloat	3956326119	USD
CY2021Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	24537415	shares
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	687525000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	531139000	USD
CY2020Q4	us-gaap	Short Term Investments ShortTermInvestments	54000	USD
CY2019Q4	us-gaap	Short Term Investments ShortTermInvestments	44000	USD
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	45237000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	42043000	USD
CY2020Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	232760000	USD
CY2019Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	202309000	USD
CY2020Q4	us-gaap	Inventory Net InventoryNet	258002000	USD
CY2019Q4	us-gaap	Inventory Net InventoryNet	237507000	USD
CY2020Q4	us-gaap	Prepaid Taxes PrepaidTaxes	3029000	USD
CY2019Q4	us-gaap	Prepaid Taxes PrepaidTaxes	4831000	USD
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CY2020Q4	us-gaap	Goodwill Goodwill	816812000	USD
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CY2020Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	19186000	USD
CY2019Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	14122000	USD
CY2020Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	0	USD
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CY2020Q4	us-gaap	Minority Interest MinorityInterest	131000	USD
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CY2019	us-gaap	Interest Expense InterestExpense	22266000	USD
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CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	863000	USD
CY2020	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	5083000	USD
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CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	31267000	USD
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CY2020	us-gaap	Profit Loss ProfitLoss	129986000	USD
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CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	5.60
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CY2018	us-gaap	Profit Loss ProfitLoss	164565000	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	5.33
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CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	24818000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	25235000	shares
CY2020	us-gaap	Profit Loss ProfitLoss	129986000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	139082000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	164565000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	8087000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-877000	USD
CY2020	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent	31761000	USD
CY2019	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent	-812000	USD
CY2018	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent	-25338000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	145652000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	130183000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	140104000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	129986000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	139082000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	164565000	USD
CY2020	us-gaap	Depreciation Depreciation	56139000	USD
CY2019	us-gaap	Depreciation Depreciation	52477000	USD
CY2018	us-gaap	Depreciation Depreciation	51003000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	40039000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	40026000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	52190000	USD
CY2020	us-gaap	Asset Impairment Charges AssetImpairmentCharges	36078000	USD
CY2019	us-gaap	Asset Impairment Charges AssetImpairmentCharges	322000	USD
CY2018	us-gaap	Asset Impairment Charges AssetImpairmentCharges	2218000	USD
CY2020	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	-593000	USD
CY2019	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	-318000	USD
CY2018	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	3965000	USD
CY2020	lfus	Non Cash Inventory Charges NonCashInventoryCharges	0	USD
CY2019	lfus	Non Cash Inventory Charges NonCashInventoryCharges	0	USD
CY2018	lfus	Non Cash Inventory Charges NonCashInventoryCharges	36927000	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	18129000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	19046000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	27431000	USD
CY2020	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	4663000	USD
CY2019	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	-4854000	USD
CY2018	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	670000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-3214000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1147000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-4679000	USD
CY2020	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	18230000	USD
CY2019	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-6638000	USD
CY2018	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-620000	USD
CY2020	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	25588000	USD
CY2019	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-28497000	USD
CY2018	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	3539000	USD
CY2020	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	12425000	USD
CY2019	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-22094000	USD
CY2018	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	33971000	USD
CY2020	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	28820000	USD
CY2019	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	-22574000	USD
CY2018	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	13708000	USD
CY2020	us-gaap	Increase Decrease In Accrued Liabilities IncreaseDecreaseInAccruedLiabilities	6765000	USD
CY2019	us-gaap	Increase Decrease In Accrued Liabilities IncreaseDecreaseInAccruedLiabilities	-54242000	USD
CY2018	us-gaap	Increase Decrease In Accrued Liabilities IncreaseDecreaseInAccruedLiabilities	29329000	USD
CY2020	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	-6788000	USD
CY2019	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	-10573000	USD
CY2018	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	7269000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	258031000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	245328000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	331828000	USD
CY2020	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	0	USD
CY2019	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	775000	USD
CY2018	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	318474000	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Shortterm Investments ProceedsFromMaturitiesPrepaymentsAndCallsOfShorttermInvestments	0	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Shortterm Investments ProceedsFromMaturitiesPrepaymentsAndCallsOfShorttermInvestments	0	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Shortterm Investments ProceedsFromMaturitiesPrepaymentsAndCallsOfShorttermInvestments	1407000	USD
CY2020	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	56191000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	61895000	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	74753000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-382248000	USD
CY2020	us-gaap	Proceeds From Long Term Lines Of Credit ProceedsFromLongTermLinesOfCredit	240000000	USD
CY2020	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	4758000	USD
CY2019	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	6213000	USD
CY2018	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	9572000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-51433000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-56457000	USD
CY2019	us-gaap	Proceeds From Long Term Lines Of Credit ProceedsFromLongTermLinesOfCredit	0	USD
CY2018	us-gaap	Proceeds From Long Term Lines Of Credit ProceedsFromLongTermLinesOfCredit	60000000	USD
CY2020	us-gaap	Repayments Of Long Term Lines Of Credit RepaymentsOfLongTermLinesOfCredit	110000000	USD
CY2019	us-gaap	Repayments Of Long Term Lines Of Credit RepaymentsOfLongTermLinesOfCredit	0	USD
CY2018	us-gaap	Repayments Of Long Term Lines Of Credit RepaymentsOfLongTermLinesOfCredit	60000000	USD
CY2020	us-gaap	Proceeds From Issuance Of Unsecured Debt ProceedsFromIssuanceOfUnsecuredDebt	0	USD
CY2019	us-gaap	Proceeds From Issuance Of Unsecured Debt ProceedsFromIssuanceOfUnsecuredDebt	0	USD
CY2018	us-gaap	Proceeds From Issuance Of Unsecured Debt ProceedsFromIssuanceOfUnsecuredDebt	75000000	USD
CY2020	us-gaap	Repayments Of Unsecured Debt RepaymentsOfUnsecuredDebt	145000000	USD
CY2019	us-gaap	Repayments Of Unsecured Debt RepaymentsOfUnsecuredDebt	10000000	USD
CY2018	us-gaap	Repayments Of Unsecured Debt RepaymentsOfUnsecuredDebt	42500000	USD
CY2020	us-gaap	Proceeds From Notes Payable ProceedsFromNotesPayable	0	USD
CY2019	us-gaap	Proceeds From Notes Payable ProceedsFromNotesPayable	0	USD
CY2018	us-gaap	Proceeds From Notes Payable ProceedsFromNotesPayable	175000000	USD
CY2020	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	18744000	USD
CY2019	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	7800000	USD
CY2018	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	18857000	USD
CY2020	us-gaap	Payments Of Dividends PaymentsOfDividends	46839000	USD
CY2019	us-gaap	Payments Of Dividends PaymentsOfDividends	44689000	USD
CY2018	us-gaap	Payments Of Dividends PaymentsOfDividends	39993000	USD
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	22927000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	99387000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	63564000	USD
CY2020	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	1786000	USD
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	USD
CY2018	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	903000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-67808000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-146276000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	121897000	USD
CY2020	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	17596000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-1189000	USD
CY2018	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-11420000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	156386000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	41406000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	60057000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	531139000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	489733000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	429676000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	687525000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	531139000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	489733000	USD
CY2018	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	26109000	USD
CY2018	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	472301000	USD
CY2020	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	6126000	USD
CY2019	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	11110000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	20095000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	21240000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	18462000	USD
CY2020	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	27619000	USD
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	40518000	USD
CY2018	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	41904000	USD
CY2018	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	0	USD
CY2017Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	927556000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	164565000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-24461000	USD
CY2018	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	27431000	USD
CY2018	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	6000	USD
CY2018	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	36482	shares
CY2018	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	7252000	USD
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	67908000	USD
CY2018	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.60
CY2020	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	2992000	USD
CY2020	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	21736000	USD
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	39993000	USD
CY2018Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1478342000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	139082000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-8899000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	19046000	USD
CY2019	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	25940	shares
CY2019	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	4957000	USD
CY2019	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	13124000	USD
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	95036000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.82
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	44688000	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1496014000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	129986000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	15666000	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	18129000	USD
CY2020	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	20250	shares
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	22927000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.92
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	46839000	USD
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1608773000	USD
CY2020	us-gaap	Fiscal Period FiscalPeriod	<div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Fiscal Year</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%"> </span></div><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> </span></div>References herein to “2020”, “fiscal 2020” or “fiscal year 2020” refer to the fiscal year ended December 26, 2020. References herein to “2019”, “fiscal 2019” or “fiscal year 2019” refer to the fiscal year ended December 28, 2019. References herein to “2018”, “fiscal 2018” or “fiscal year 2018” refer to the fiscal year ended December 29, 2018. The Company operates on a 52-53 week fiscal year (4-4-5 basis) ending on the Saturday closest to December 31.
CY2020	us-gaap	Use Of Estimates UseOfEstimates	<div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Use of Estimates</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%"> </span></div><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> </span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The process of preparing financial statements in conformity with generally accepted accounting principles in the United States of America requires management to make estimates and assumptions that affect the amounts of assets and liabilities at the date of the Consolidated Financial Statements, and the reported amounts of revenues and expenses and the accompanying notes. The Company evaluates and updates its assumptions and estimates on an ongoing basis and may employ outside experts to assist in its evaluation, as considered necessary. Actual results could differ from those estimates.</span></div>
CY2020	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	0	USD
CY2018	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-600000	USD
CY2020Q4	us-gaap	Equity Method Investments EquityMethodInvestments	11400000	USD
CY2019Q4	us-gaap	Equity Method Investments EquityMethodInvestments	11100000	USD
CY2020	us-gaap	Number Of Reporting Units NumberOfReportingUnits	7	reporting_unit
CY2020	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	1445695000	USD
CY2020Q2	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	33800000	USD
CY2018	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	215228000	USD
CY2019	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	1503873000	USD
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable Noncurrent AllowanceForDoubtfulAccountsReceivableNoncurrent	1400000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable Noncurrent AllowanceForDoubtfulAccountsReceivableNoncurrent	1300000	USD
CY2020	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	14900000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-5200000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	900000	USD
CY2020Q4	us-gaap	Loss Contingency Accrual Carrying Value Noncurrent LossContingencyAccrualCarryingValueNoncurrent	2300000	EUR
CY2020Q4	us-gaap	Loss Contingency Accrual Carrying Value Noncurrent LossContingencyAccrualCarryingValueNoncurrent	2900000	USD
CY2019Q4	us-gaap	Loss Contingency Accrual Carrying Value Noncurrent LossContingencyAccrualCarryingValueNoncurrent	1000000.0	EUR
CY2019Q4	us-gaap	Loss Contingency Accrual Carrying Value Noncurrent LossContingencyAccrualCarryingValueNoncurrent	1100000	USD
CY2018Q4	us-gaap	Tax Cuts And Jobs Act Of2017 Income Tax Expense Benefit TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit	3200000	USD
CY2018Q1	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2018Q1	us-gaap	Share Price SharePrice	207.5
CY2020	lfus	Income Tax Expense Benefit Continuing Operations Adjustment Of Deferred Tax Asset Liability Toll Charge Noncurrent IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiabilityTollChargeNoncurrent	-20800000	USD
CY2020	lfus	Income Tax Expense Benefit Continuing Operations Adjustmentof Deferred Tax Asset Liability Toll Charge Current IncomeTaxExpenseBenefitContinuingOperationsAdjustmentofDeferredTaxAssetLiabilityTollChargeCurrent	-3000000.0	USD
CY2018	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	1735181000	USD
CY2018	lfus	Business Acquisition Pro Forma Income Lossfrom Continuing Operationsbefore Tax BusinessAcquisitionProFormaIncomeLossfromContinuingOperationsbeforeTax	272724000	USD
CY2018	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	8.61
CY2018	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	8.53
CY2018	lfus	Inventory Amortization Period InventoryAmortizationPeriod	P5M
CY2020Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	85394000	USD
CY2019Q4	us-gaap	Inventory Raw Materials And Supplies InventoryRawMaterialsAndSupplies	76732000	USD
CY2020Q4	us-gaap	Inventory Work In Process InventoryWorkInProcess	92783000	USD
CY2019Q4	us-gaap	Inventory Work In Process InventoryWorkInProcess	84561000	USD
CY2020Q4	us-gaap	Inventory Finished Goods InventoryFinishedGoods	114641000	USD
CY2019Q4	us-gaap	Inventory Finished Goods InventoryFinishedGoods	110388000	USD
CY2020Q4	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	34816000	USD
CY2019Q4	us-gaap	Inventory Valuation Reserves InventoryValuationReserves	34174000	USD
CY2020Q4	us-gaap	Inventory Net InventoryNet	258002000	USD
CY2019Q4	us-gaap	Inventory Net InventoryNet	237507000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	480390000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	419915000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	344178000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	344617000	USD
CY2020	us-gaap	Depreciation Depreciation	56100000	USD
CY2019	us-gaap	Depreciation Depreciation	52500000	USD
CY2018	us-gaap	Depreciation Depreciation	51000000.0	USD
CY2018Q4	us-gaap	Goodwill Gross GoodwillGross	835201000	USD
CY2018Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	8486000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	826715000	USD
CY2019	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	-6126000	USD
CY2019Q4	us-gaap	Goodwill Gross GoodwillGross	829383000	USD
CY2019Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	8794000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	820589000	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	33841000	USD
CY2020	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	30064000	USD
CY2020Q4	us-gaap	Goodwill Gross GoodwillGross	862230000	USD
CY2020Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	45418000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	816812000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	40000000.0	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	40000000.0	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	563464000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	271577000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	291887000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	544586000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	223339000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	321247000	USD
CY2018	us-gaap	Finitelived Intangible Assets Acquired1 FinitelivedIntangibleAssetsAcquired1	212700000	USD
CY2018	us-gaap	Finitelived Intangible Assets Acquired1 FinitelivedIntangibleAssetsAcquired1	212720000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	52200000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	38858000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	37851000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	33279000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	30121000	USD
CY2020Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	50689000	USD
CY2019Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	40774000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	29689000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense After Year Five FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive	122089000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	291887000	USD
CY2020Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	6811000	USD
CY2019Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	7259000	USD
CY2020Q4	us-gaap	Interest And Dividends Payable Current InterestAndDividendsPayableCurrent	4517000	USD
CY2019Q4	us-gaap	Interest And Dividends Payable Current InterestAndDividendsPayableCurrent	5058000	USD
CY2019Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	1106000	USD
CY2020Q4	us-gaap	Restructuring Reserve Current RestructuringReserveCurrent	4195000	USD
CY2019Q4	us-gaap	Restructuring Reserve Current RestructuringReserveCurrent	2679000	USD
CY2020Q4	lfus	Other Customer Reserves OtherCustomerReserves	3858000	USD
CY2019Q4	lfus	Other Customer Reserves OtherCustomerReserves	1143000	USD
CY2020Q4	us-gaap	Accrued Professional Fees Current AccruedProfessionalFeesCurrent	3321000	USD
CY2019Q4	us-gaap	Accrued Professional Fees Current AccruedProfessionalFeesCurrent	3986000	USD
CY2020Q4	us-gaap	Deferred Revenue DeferredRevenue	2959000	USD
CY2019Q4	us-gaap	Deferred Revenue DeferredRevenue	828000	USD
CY2020Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	2751000	USD
CY2020Q4	us-gaap	Accrual For Taxes Other Than Income Taxes Current AccrualForTaxesOtherThanIncomeTaxesCurrent	2126000	USD
CY2019Q4	us-gaap	Accrual For Taxes Other Than Income Taxes Current AccrualForTaxesOtherThanIncomeTaxesCurrent	1940000	USD
CY2020Q4	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	29251000	USD
CY2019Q4	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	19347000	USD
CY2020Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	110478000	USD
CY2019Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	84120000	USD
CY2020Q4	lfus	Lessor Operating Lease Number Of Renewal Options LessorOperatingLeaseNumberOfRenewalOptions	1	renewal
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	17615000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	21918000	USD
CY2020Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	6811000	USD
CY2019Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	7259000	USD
CY2020Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	12950000	USD
CY2019Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	17166000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	19761000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	24425000	USD
CY2020	us-gaap	Short Term Lease Cost ShortTermLeaseCost	512000	USD
CY2019	us-gaap	Short Term Lease Cost ShortTermLeaseCost	562000	USD
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	1307000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	916000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	8591000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	8664000	USD
CY2020	us-gaap	Operating Lease Expense OperatingLeaseExpense	10410000	USD
CY2019	us-gaap	Operating Lease Expense OperatingLeaseExpense	10142000	USD
CY2020	us-gaap	Operating Lease Expense OperatingLeaseExpense	10400000	USD
CY2019	us-gaap	Operating Lease Expense OperatingLeaseExpense	10100000	USD
CY2018	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	9600000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	7660000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	6162000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	3952000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	3350000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	262000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	302000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	21688000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	19761000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P3Y4M28D
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P4Y18D
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0506
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0511
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	8929000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	2862000	USD
CY2020	us-gaap	Restructuring Charges RestructuringCharges	5638000	USD
CY2020	us-gaap	Asset Impairment Charges AssetImpairmentCharges	36078000	USD
CY2020	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	41716000	USD
CY2019	us-gaap	Restructuring Charges RestructuringCharges	12711000	USD
CY2019	us-gaap	Asset Impairment Charges AssetImpairmentCharges	322000	USD
CY2019	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	13033000	USD
CY2018	us-gaap	Restructuring Charges RestructuringCharges	10365000	USD
CY2018	us-gaap	Asset Impairment Charges AssetImpairmentCharges	2218000	USD
CY2018	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	12583000	USD
CY2020	us-gaap	Restructuring Charges RestructuringCharges	5600000	USD
CY2020	us-gaap	Asset Impairment Charges AssetImpairmentCharges	36100000	USD
CY2019	us-gaap	Restructuring Charges RestructuringCharges	12700000	USD
CY2018	us-gaap	Restructuring Charges RestructuringCharges	10400000	USD
CY2020Q4	us-gaap	Restructuring Reserve RestructuringReserve	4200000	USD
CY2019Q4	us-gaap	Restructuring Reserve RestructuringReserve	2700000	USD
CY2020Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	4114000	USD
CY2019Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	3669000	USD
CY2020Q4	us-gaap	Long Term Debt LongTermDebt	687034000	USD
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	679158000	USD
CY2020Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	0	USD
CY2019Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	10000000	USD
CY2020Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	687034000	USD
CY2019Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	669158000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	20100000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	21200000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	18500000	USD
CY2020Q1	us-gaap	Proceeds From Long Term Lines Of Credit ProceedsFromLongTermLinesOfCredit	100000000.0	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	0	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	27619000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	142679000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	0	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	180000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	340850000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents Fair Value Disclosure CashAndCashEquivalentsFairValueDisclosure	118999000	USD
CY2019Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	12969000	USD
CY2019Q4	us-gaap	Trading Securities Debt TradingSecuritiesDebt	10464000	USD
CY2020Q4	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	691148000	USD
CY2020	us-gaap	Gain Loss On Sale Of Derivatives GainLossOnSaleOfDerivatives	200000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents Fair Value Disclosure CashAndCashEquivalentsFairValueDisclosure	73461000	USD
CY2020Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	19186000	USD
CY2020Q4	us-gaap	Trading Securities Debt TradingSecuritiesDebt	13249000	USD
CY2020Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	105896000	USD
CY2019Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	142432000	USD
CY2020Q1	us-gaap	Other Asset Impairment Charges OtherAssetImpairmentCharges	1900000	USD
CY2020Q2	lfus	Defined Benefit Plan Estimated Reduction In Pension Benefit Obligation From Group Annuity Contract DefinedBenefitPlanEstimatedReductionInPensionBenefitObligationFromGroupAnnuityContract	55000000	USD
CY2020Q2	lfus	Defined Benefit Plan Estimated Reduction In Pension Benefit Obligation From Group Annuity Contract Percent DefinedBenefitPlanEstimatedReductionInPensionBenefitObligationFromGroupAnnuityContractPercent	0.37
CY2020Q2	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	13400000	USD
CY2020Q2	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	10400000	USD
CY2020Q2	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	8400000	GBP
CY2020Q4	us-gaap	Defined Benefit Plan Assets For Plan Benefits Noncurrent DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent	39000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Assets For Plan Benefits Noncurrent DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent	885000	USD
CY2020Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	2751000	USD
CY2019Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	1106000	USD
CY2020Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	45802000	USD
CY2019Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	38198000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Amounts Recognized In Balance Sheet DefinedBenefitPlanAmountsRecognizedInBalanceSheet	-48514000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Amounts Recognized In Balance Sheet DefinedBenefitPlanAmountsRecognizedInBalanceSheet	-38419000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Net Gains Losses Before Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax	-37285000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Net Gains Losses Before Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax	-15635000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Net Prior Service Cost Credit Before Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax	3937000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Net Prior Service Cost Credit Before Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax	4273000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Before Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax	41222000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Before Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax	19908000	USD
CY2020	us-gaap	Defined Benefit Plan Amortization Of Prior Service Cost Credit DefinedBenefitPlanAmortizationOfPriorServiceCostCredit	181000	USD
CY2020	lfus	Defined Benefit Plan Amortizationof Net Actuarial Cost DefinedBenefitPlanAmortizationofNetActuarialCost	782000	USD
CY2020	us-gaap	Other Comprehensive Income Defined Benefit Plan Net Prior Service Cost Credit Arising During Period Before Tax OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax	324000	USD
CY2020	us-gaap	Defined Benefit Plan Actuarial Gain Loss Immediate Recognition As Component In Net Periodic Benefit Cost Credit DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit	19861000	USD
CY2020	us-gaap	Defined Benefit Plan Recognized Net Gain Loss Due To Settlements And Curtailments1 DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1	-236000	USD
CY2020	lfus	Defined Benefit Plan Foreign Currency Adjustments Immediate Recognitionas Componentin Net Periodic Benefit Cost Credit DefinedBenefitPlanForeignCurrencyAdjustmentsImmediateRecognitionasComponentinNetPeriodicBenefitCostCredit	-1298000	USD
CY2020	lfus	Defined Benefit Plan Immediate Recognitionas Componentin Net Periodic Benefit Cost Credit DefinedBenefitPlanImmediateRecognitionasComponentinNetPeriodicBenefitCostCredit	-19636000	USD
CY2020Q2	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	13400000	USD
CY2020	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	2462000	USD
CY2019	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	2040000	USD
CY2018	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	2266000	USD
CY2020	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	2173000	USD
CY2019	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	3169000	USD
CY2018	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	3104000	USD
CY2020	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	1972000	USD
CY2019	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	3187000	USD
CY2018	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	3222000	USD
CY2020	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-963000	USD
CY2018	us-gaap	Defined Benefit Plan Recognized Net Gain Loss Due To Settlements And Curtailments1 DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1	-238000	USD
CY2020	us-gaap	Pension Expense PensionExpense	3862000	USD
CY2019	us-gaap	Pension Expense PensionExpense	2525000	USD
CY2019	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-243000	USD
CY2018	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-291000	USD
CY2020	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	3626000	USD
CY2019	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	2265000	USD
CY2018	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	2439000	USD
CY2020	us-gaap	Defined Benefit Plan Recognized Net Gain Loss Due To Settlements And Curtailments1 DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1	-236000	USD
CY2019	us-gaap	Defined Benefit Plan Recognized Net Gain Loss Due To Settlements And Curtailments1 DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1	-260000	USD
CY2018	us-gaap	Pension Expense PensionExpense	2677000	USD
CY2020	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.023
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.031
CY2018	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.028
CY2020	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.037
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.045
CY2018	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.042
CY2020	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease	0.047
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease	0.046
CY2018	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease	0.050
CY2020Q4	us-gaap	Defined Benefit Plan Pension Plan With Projected Benefit Obligation In Excess Of Plan Assets Projected Benefit Obligation DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsProjectedBenefitObligation	148992000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Pension Plan With Projected Benefit Obligation In Excess Of Plan Assets Projected Benefit Obligation DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsProjectedBenefitObligation	81362000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Pension Plan With Projected Benefit Obligation In Excess Of Plan Assets Plan Assets DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsPlanAssets	100439000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Pension Plan With Projected Benefit Obligation In Excess Of Plan Assets Plan Assets DefinedBenefitPlanPensionPlanWithProjectedBenefitObligationInExcessOfPlanAssetsPlanAssets	42058000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets Aggregate Accumulated Benefit Obligation DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateAccumulatedBenefitObligation	130453000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets Aggregate Accumulated Benefit Obligation DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateAccumulatedBenefitObligation	75744000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets Aggregate Fair Value Of Plan Assets DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateFairValueOfPlanAssets	92248000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets Aggregate Fair Value Of Plan Assets DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateFairValueOfPlanAssets	42058000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.012
CY2019Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.023
CY2018Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.031
CY2020Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease	0.049
CY2019Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease	0.047
CY2018Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Rate Of Compensation Increase DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease	0.046
CY2020Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Next Twelve Months DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths	6562000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Two DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo	4718000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Three DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree	4902000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Four DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour	4742000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Five DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive	5357000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Five Fiscal Years Thereafter DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter	31164000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Expected Future Employer Contributions Next Fiscal Year DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear	2200000	USD
CY2020	lfus	Defined Benefit Plan Expected Direct Payments Next Fiscal Year DefinedBenefitPlanExpectedDirectPaymentsNextFiscalYear	3800000	USD
CY2020	us-gaap	Pension And Other Postretirement Benefit Expense PensionAndOtherPostretirementBenefitExpense	2000000.0	USD
CY2019	us-gaap	Pension And Other Postretirement Benefit Expense PensionAndOtherPostretirementBenefitExpense	1400000	USD
CY2018	us-gaap	Pension And Other Postretirement Benefit Expense PensionAndOtherPostretirementBenefitExpense	1800000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	3500000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	2800000	USD
CY2020	us-gaap	Amount Recognized In Net Periodic Benefit Cost And Other Comprehensive Income Loss Before Tax AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax	100000	USD
CY2019	us-gaap	Amount Recognized In Net Periodic Benefit Cost And Other Comprehensive Income Loss Before Tax AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax	600000	USD
CY2020	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.037
CY2020Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	1
CY2019Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	1
CY2020Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	100478000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	78502000	USD
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized	900000	shares
CY2020	lfus	Sharebased Compensation Arrangementby Sharebased Payment Award Options Convertedin Period SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsConvertedinPeriod	499027	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	600465	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	131.32
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	297954	shares
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	152.86
CY2020	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	209093	shares
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	104.18
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod	22377	shares
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice	173.95
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	666949	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	148.01
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y1M6D
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	69126000	USD
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber	296409	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	133.00
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1	P3Y8M12D
CY2020Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	35172000	USD
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	20600000	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	12500000	USD
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	38300000	USD
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue	20800000	USD
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Share Based Liabilities Paid ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid	500000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	3100000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	3300000	USD
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue	9500000	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue	15500000	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Share Based Liabilities Paid ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid	900000	USD
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Share Based Liabilities Paid ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid	1100000	USD
CY2020Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	22600000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P2Y
CY2020	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	19100000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	19900000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	28200000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	6000000.0	USD
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	38.09
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	47.63
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	45.19
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.0030
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.0233
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.0279
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate	0.0127
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate	0.0086
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate	0.0077
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.330
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.270
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.250
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P4Y8M12D
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P4Y4M24D
CY2018	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P4Y4M24D
CY2020	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	175110	shares
CY2019	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	579916	shares
CY2018	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	391972	shares
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	22900000	USD
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	95000000.0	USD
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	67900000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	15194000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	472000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	15666000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-10625000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	1726000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-8899000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-24414000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-47000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-24461000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-24461000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-8899000	USD
CY2018Q4	us-gaap	Tax Cuts And Jobs Act Of2017 Income Tax Expense Benefit TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit	3200000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	15666000	USD
CY2020Q2	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	13400000	USD
CY2020	lfus	Income Tax Expense Benefit Continuing Operations Adjustment Of Deferred Tax Asset Liability Toll Charge Noncurrent IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiabilityTollChargeNoncurrent	-20800000	USD
CY2020	lfus	Income Tax Expense Benefit Continuing Operations Adjustmentof Deferred Tax Asset Liability Toll Charge Current IncomeTaxExpenseBenefitContinuingOperationsAdjustmentofDeferredTaxAssetLiabilityTollChargeCurrent	-3000000.0	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	-16732000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	-11970000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	-49995000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	177985000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	177854000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	254937000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	161253000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	165884000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	204942000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	437000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	-3495000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	-3193000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	203000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	834000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	119000	USD
CY2020	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	33841000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	30610000	USD
CY2018	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	48130000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	34481000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	27949000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	45056000	USD
CY2020	us-gaap	Deferred Federal State And Local Tax Expense Benefit DeferredFederalStateAndLocalTaxExpenseBenefit	-5354000	USD
CY2019	us-gaap	Deferred Federal State And Local Tax Expense Benefit DeferredFederalStateAndLocalTaxExpenseBenefit	1839000	USD
CY2018	us-gaap	Deferred Federal State And Local Tax Expense Benefit DeferredFederalStateAndLocalTaxExpenseBenefit	-3896000	USD
CY2020	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	2140000	USD
CY2019	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-2986000	USD
CY2018	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-783000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-3214000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1147000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-4679000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	31267000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26802000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	40377000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	3300000	USD
CY2020	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	33863000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	34836000	USD
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	43038000	USD
CY2020	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-19730000	USD
CY2019	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-22457000	USD
CY2018	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-20472000	USD
CY2020	lfus	Tax Impact On Non Deductible Goodwill Impairment Charge TaxImpactOnNonDeductibleGoodwillImpairmentCharge	5642000	USD
CY2019	lfus	Tax Impact On Non Deductible Goodwill Impairment Charge TaxImpactOnNonDeductibleGoodwillImpairmentCharge	0	USD
CY2018	lfus	Tax Impact On Non Deductible Goodwill Impairment Charge TaxImpactOnNonDeductibleGoodwillImpairmentCharge	0	USD
CY2020	lfus	Effective Income Tax Reconciliation Undistributed Foreign Earnings EffectiveIncomeTaxReconciliationUndistributedForeignEarnings	3955000	USD
CY2019	lfus	Effective Income Tax Reconciliation Undistributed Foreign Earnings EffectiveIncomeTaxReconciliationUndistributedForeignEarnings	2136000	USD
CY2018	lfus	Effective Income Tax Reconciliation Undistributed Foreign Earnings EffectiveIncomeTaxReconciliationUndistributedForeignEarnings	4660000	USD
CY2020	lfus	Effective Income Tax Rate Reconciliation Impactof Tax Provisions Amount EffectiveIncomeTaxRateReconciliationImpactofTaxProvisionsAmount	3731000	USD
CY2019	lfus	Effective Income Tax Rate Reconciliation Impactof Tax Provisions Amount EffectiveIncomeTaxRateReconciliationImpactofTaxProvisionsAmount	6469000	USD
CY2018	lfus	Effective Income Tax Rate Reconciliation Impactof Tax Provisions Amount EffectiveIncomeTaxRateReconciliationImpactofTaxProvisionsAmount	5075000	USD
CY2020	lfus	Effective Income Tax Reconciliation Non Us Losses And Expenses With No Tax Benefits EffectiveIncomeTaxReconciliationNonUSLossesAndExpensesWithNoTaxBenefits	2774000	USD
CY2019	lfus	Effective Income Tax Reconciliation Non Us Losses And Expenses With No Tax Benefits EffectiveIncomeTaxReconciliationNonUSLossesAndExpensesWithNoTaxBenefits	6570000	USD
CY2018	lfus	Effective Income Tax Reconciliation Non Us Losses And Expenses With No Tax Benefits EffectiveIncomeTaxReconciliationNonUSLossesAndExpensesWithNoTaxBenefits	3107000	USD
CY2020	lfus	Effective Income Tax Rate Reconciliation Changein Unrecognized Tax Benefitsand Related Accrued Interest EffectiveIncomeTaxRateReconciliationChangeinUnrecognizedTaxBenefitsandRelatedAccruedInterest	2160000	USD
CY2019	lfus	Effective Income Tax Rate Reconciliation Changein Unrecognized Tax Benefitsand Related Accrued Interest EffectiveIncomeTaxRateReconciliationChangeinUnrecognizedTaxBenefitsandRelatedAccruedInterest	-1468000	USD
CY2018	lfus	Effective Income Tax Rate Reconciliation Changein Unrecognized Tax Benefitsand Related Accrued Interest EffectiveIncomeTaxRateReconciliationChangeinUnrecognizedTaxBenefitsandRelatedAccruedInterest	208000	USD
CY2020	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	-584000	USD
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	1080000	USD
CY2018	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	-1238000	USD
CY2020	lfus	Effective Income Tax Reconciliation Nondeductible Professional Fees EffectiveIncomeTaxReconciliationNondeductibleProfessionalFees	236000	USD
CY2019	lfus	Effective Income Tax Reconciliation Nondeductible Professional Fees EffectiveIncomeTaxReconciliationNondeductibleProfessionalFees	195000	USD
CY2018	lfus	Effective Income Tax Reconciliation Nondeductible Professional Fees EffectiveIncomeTaxReconciliationNondeductibleProfessionalFees	1001000	USD
CY2020	lfus	Effective Income Tax Rate Reconciliation Toll Charge Amount EffectiveIncomeTaxRateReconciliationTollChargeAmount	0	USD
CY2019	lfus	Effective Income Tax Rate Reconciliation Toll Charge Amount EffectiveIncomeTaxRateReconciliationTollChargeAmount	0	USD
CY2018	lfus	Effective Income Tax Rate Reconciliation Toll Charge Amount EffectiveIncomeTaxRateReconciliationTollChargeAmount	2278000	USD
CY2020	lfus	Effective Income Tax Rate Reconciliation Provisional Tax Act Impact Other Than Toll Charge Amount EffectiveIncomeTaxRateReconciliationProvisionalTaxActImpactOtherThanTollChargeAmount	0	USD
CY2019	lfus	Effective Income Tax Rate Reconciliation Provisional Tax Act Impact Other Than Toll Charge Amount EffectiveIncomeTaxRateReconciliationProvisionalTaxActImpactOtherThanTollChargeAmount	0	USD
CY2018	lfus	Effective Income Tax Rate Reconciliation Provisional Tax Act Impact Other Than Toll Charge Amount EffectiveIncomeTaxRateReconciliationProvisionalTaxActImpactOtherThanTollChargeAmount	966000	USD
CY2020	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-780000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-559000	USD
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	1754000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	31267000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26802000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	40377000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	31123000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	28294000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	24763000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	10511000	USD
CY2020Q4	us-gaap	Deferred Tax Asset Interest Carryforward DeferredTaxAssetInterestCarryforward	10352000	USD
CY2019Q4	us-gaap	Deferred Tax Asset Interest Carryforward DeferredTaxAssetInterestCarryforward	5324000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards Research DeferredTaxAssetsTaxCreditCarryforwardsResearch	3724000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards Research DeferredTaxAssetsTaxCreditCarryforwardsResearch	2581000	USD
CY2020Q4	lfus	Deferred Tax Assets Capitalized Expense DeferredTaxAssetsCapitalizedExpense	4178000	USD
CY2019Q4	lfus	Deferred Tax Assets Capitalized Expense DeferredTaxAssetsCapitalizedExpense	2400000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards Foreign DeferredTaxAssetsTaxCreditCarryforwardsForeign	772000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards Foreign DeferredTaxAssetsTaxCreditCarryforwardsForeign	1320000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards Other DeferredTaxAssetsTaxCreditCarryforwardsOther	117000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards Other DeferredTaxAssetsTaxCreditCarryforwardsOther	1261000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	61898000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	75029000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	51691000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	13131000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	5957000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	45734000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssets	76472000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssets	71229000	USD
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CY2019Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	12968000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Unrealized Currency Transaction Gains DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGains	5719000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Unrealized Currency Transaction Gains DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGains	0	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	4394000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	3231000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	100808000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	87428000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	38910000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	41694000	USD
CY2020	us-gaap	Income Taxes Paid IncomeTaxesPaid	35200000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	47600000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	46200000	USD
CY2020	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	7600000	USD
CY2019	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	7100000	USD
CY2018	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	4300000	USD
CY2020Q4	us-gaap	Undistributed Earnings Of Foreign Subsidiaries UndistributedEarningsOfForeignSubsidiaries	767000000	USD
CY2020Q4	lfus	Deferred Tax Liabilities Recognizedon Undistributed Foreign Earnings DeferredTaxLiabilitiesRecognizedonUndistributedForeignEarnings	14200000	USD
CY2019Q4	lfus	Deferred Tax Liabilities Recognizedon Undistributed Foreign Earnings DeferredTaxLiabilitiesRecognizedonUndistributedForeignEarnings	13000000.0	USD
CY2020	lfus	Income Tax Holiday Expense Benefit Amount Per Diluted Share IncomeTaxHolidayExpenseBenefitAmountPerDilutedShare	0.17
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	18259000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	1305000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	2758000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	17400000	USD
CY2019	lfus	Unrecognized Tax Benefits Decrease Resulting From Other Positions UnrecognizedTaxBenefitsDecreaseResultingFromOtherPositions	85000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	16721000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	700000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	103000	USD
CY2020	lfus	Unrecognized Tax Benefits Increase Resulting From Other Positions UnrecognizedTaxBenefitsIncreaseResultingFromOtherPositions	119000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	17437000	USD
CY2020	us-gaap	Income Tax Examination Interest Expense IncomeTaxExaminationInterestExpense	1600000	USD
CY2019	us-gaap	Income Tax Examination Interest Expense IncomeTaxExaminationInterestExpense	1300000	USD
CY2019	lfus	Income Tax Examination Decrease Dueto Lapseof Statuteof Limitations IncomeTaxExaminationDecreaseDuetoLapseofStatuteofLimitations	600000	USD
CY2018	us-gaap	Income Tax Examination Interest Expense IncomeTaxExaminationInterestExpense	1500000	USD
CY2018	lfus	Income Tax Examination Decrease Dueto Lapseof Statuteof Limitations IncomeTaxExaminationDecreaseDuetoLapseofStatuteofLimitations	300000	USD
CY2020Q4	us-gaap	Income Tax Examination Interest Accrued IncomeTaxExaminationInterestAccrued	8800000	USD
CY2019Q4	us-gaap	Income Tax Examination Interest Accrued IncomeTaxExaminationInterestAccrued	7200000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	16700000	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	5.33
CY2020	us-gaap	Profit Loss ProfitLoss	129986000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	139082000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	164565000	USD
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	24371000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	24576000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	24870000	shares
CY2020	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	221000	shares
CY2019	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	242000	shares
CY2018	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	365000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	24592000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	24818000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	25235000	shares
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	5.66
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.62
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	5.29
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	5.60
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.52
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	222526	shares
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	129658	shares
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	42305	shares
CY2020	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	175110	shares
CY2019	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	579916	shares
CY2018	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	391972	shares
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	22900000	USD
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	95000000.0	USD
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	67900000	USD
CY2020	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	3	segment
CY2020	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	1445695000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	225049000	USD
CY2020	us-gaap	Interest Expense InterestExpense	21077000	USD
CY2019	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	1503873000	USD
CY2018	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	1718468000	USD
CY2020	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	96178000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	92503000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	103193000	USD
CY2020	us-gaap	Operating Income Loss OperatingIncomeLoss	162372000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	192791000	USD
CY2019	us-gaap	Interest Expense InterestExpense	22266000	USD
CY2018	us-gaap	Interest Expense InterestExpense	22569000	USD
CY2020	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	14875000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-5224000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	863000	USD
CY2020	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	5083000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	583000	USD
CY2018	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	1599000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	161253000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	165884000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	204942000	USD
CY2020	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	41700000	USD
CY2020Q2	us-gaap	Other Asset Impairment Charges OtherAssetImpairmentCharges	33800000	USD
CY2020	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	1445695000	USD
CY2019	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	1503873000	USD
CY2018	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	1718468000	USD
CY2020Q4	us-gaap	Noncurrent Assets NoncurrentAssets	344178000	USD
CY2019Q4	us-gaap	Noncurrent Assets NoncurrentAssets	344617000	USD
CY2018Q4	us-gaap	Noncurrent Assets NoncurrentAssets	339894000	USD
CY2020	us-gaap	Property Plant And Equipment Additions PropertyPlantAndEquipmentAdditions	51208000	USD
CY2019	us-gaap	Property Plant And Equipment Additions PropertyPlantAndEquipmentAdditions	66366000	USD
CY2018	us-gaap	Property Plant And Equipment Additions PropertyPlantAndEquipmentAdditions	74753000	USD
CY2020Q4	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	400696000	USD
CY2020Q3	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	391566000	USD
CY2020Q2	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	307337000	USD
CY2020Q1	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	346096000	USD
CY2019Q4	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	338523000	USD
CY2019Q3	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	361971000	USD
CY2019Q2	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	397879000	USD
CY2019Q1	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	405500000	USD
CY2020Q4	us-gaap	Gross Profit GrossProfit	138083000	USD
CY2020Q3	us-gaap	Gross Profit GrossProfit	138831000	USD
CY2020Q2	us-gaap	Gross Profit GrossProfit	99902000	USD
CY2020Q1	us-gaap	Gross Profit GrossProfit	124356000	USD
CY2019Q4	us-gaap	Gross Profit GrossProfit	113735000	USD
CY2019Q3	us-gaap	Gross Profit GrossProfit	132708000	USD
CY2019Q2	us-gaap	Gross Profit GrossProfit	144308000	USD
CY2019Q1	us-gaap	Gross Profit GrossProfit	155544000	USD
CY2020Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	44750000	USD
CY2019Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	32317000	USD
CY2020Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	65014000	USD
CY2020Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	64558000	USD
CY2020Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	-11950000	USD
CY2019Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	47167000	USD
CY2019Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	52634000	USD
CY2019Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	60673000	USD
CY2020Q4	us-gaap	Profit Loss ProfitLoss	58977000	USD
CY2020Q3	us-gaap	Profit Loss ProfitLoss	55356000	USD
CY2020Q2	us-gaap	Profit Loss ProfitLoss	-8991000	USD
CY2020Q1	us-gaap	Profit Loss ProfitLoss	24644000	USD
CY2019Q4	us-gaap	Profit Loss ProfitLoss	22654000	USD
CY2019Q3	us-gaap	Profit Loss ProfitLoss	35647000	USD
CY2019Q2	us-gaap	Profit Loss ProfitLoss	43792000	USD
CY2019Q1	us-gaap	Profit Loss ProfitLoss	36989000	USD
CY2020Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.41
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.27
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.37
CY2020Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.01
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.93
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.46
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.77
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.50
CY2020Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.39
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.25
CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.37
CY2020Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.00
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.92
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.44
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.75
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.48
CY2020Q4	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	700000	USD
CY2019Q4	us-gaap	Asset Impairment Charges AssetImpairmentCharges	4200000	USD
CY2020Q4	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	800000	USD
CY2020Q3	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	1300000	USD
CY2020Q3	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	300000	USD
CY2020Q3	us-gaap	Asset Impairment Charges AssetImpairmentCharges	100000	USD
CY2020Q2	us-gaap	Other Asset Impairment Charges OtherAssetImpairmentCharges	33800000	USD
CY2020Q2	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	1800000	USD
CY2020Q2	us-gaap	Increase Decrease In Coal Inventories IncreaseDecreaseInCoalInventories	1800000	USD
CY2020Q2	lfus	Asset Retirement Expense AssetRetirementExpense	200000	USD
CY2020Q2	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	100000	USD
CY2020Q1	us-gaap	Restructuring Costs RestructuringCosts	4000000.0	USD
CY2020Q1	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	1200000	USD
CY2019Q4	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	1900000	USD
CY2019Q4	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	2100000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	3300000	USD
CY2019Q3	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	3200000	USD
CY2019Q3	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	2500000	USD
CY2019Q2	us-gaap	Restructuring Costs And Asset Impairment Charges RestructuringCostsAndAssetImpairmentCharges	5700000	USD
CY2019Q2	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	1500000	USD
CY2019Q2	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	400000	USD
CY2019Q2	us-gaap	Asset Impairment Charges AssetImpairmentCharges	200000	USD
CY2019Q1	us-gaap	Asset Impairment Charges AssetImpairmentCharges	2800000	USD
CY2019Q1	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	-2600000	USD
CY2019Q1	us-gaap	Restructuring Costs RestructuringCosts	2700000	USD
CY2019Q1	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	2400000	USD
CY2019Q1	us-gaap	Business Combination Step Acquisition Equity Interest In Acquiree Remeasurement Gain BusinessCombinationStepAcquisitionEquityInterestInAcquireeRemeasurementGain	300000	USD
CY2019Q2	us-gaap	Disposal Group Not Discontinued Operation Gain Loss On Disposal DisposalGroupNotDiscontinuedOperationGainLossOnDisposal	2600000	USD

Files In Submission

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$LFUS
LITTELFUSE INC /DE Stock $lfus

2019 Q4 Form 10-K Financial Statement

#000088933121000010 Filed on February 18, 2021

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$LFUS LITTELFUSE INC /DE Stock $lfus

2019 Q4 Form 10-K Financial Statement

#000088933121000010 Filed on February 18, 2021

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Balance Sheet

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Facts In Submission

Files In Submission

$LFUS
LITTELFUSE INC /DE Stock $lfus