Debt Issuance Expense

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line of Credit, Minimum Increase To Borrowing Amount

+ References

No definition available.

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Namespace Prefix:	lfus_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number Of Series

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No definition available.

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

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Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Debt - Narrative (Details)		3 Months Ended				6 Months Ended		12 Months Ended
Debt - Narrative (Details)	Mar. 12, 2026 USD ($)	Jun. 27, 2026 USD ($)	Mar. 28, 2026 USD ($)	Jun. 28, 2025 USD ($)	Mar. 29, 2025 USD ($)	Jun. 27, 2026 USD ($)	Jun. 28, 2025 USD ($)	Dec. 30, 2023 EUR (€)	Dec. 31, 2022 USD ($)	Dec. 27, 2025 USD ($)	Jul. 18, 2022 USD ($)	Jun. 30, 2022 USD ($)	May 12, 2022 USD ($)	Jan. 16, 2018 USD ($)	Nov. 15, 2017 USD ($) series	Feb. 15, 2017 USD ($)	Dec. 08, 2016 USD ($) series	Dec. 08, 2016 EUR (€) series
Debt Instrument
Letter of credit outstanding		$ 100,000				$ 100,000
Cash paid during the period for interest		$ 2,600,000		$ 5,600,000		$ 13,091,000	$ 17,834,000
Hedged Portion \| Credit Agreement
Debt Instrument
Effective interest rate (as a percent)		3.88%				3.88%
Interest rate swap agreement \| Designated as Hedging Instrument \| Designated as cash flow hedge
Debt Instrument
Notional amount of derivatives													$ 200,000,000
Term loan
Debt Instrument
Maximum borrowing capacity, credit facility	$ 300,000,000
Repayments of debt			$ 3,800,000
Long-term debt, gross		$ 0				$ 0				$ 266,250,000
Loan minimum increments	25,000,000
Term loan \| Revolving Credit Facility
Debt Instrument
Maximum borrowing capacity, credit facility	800,000,000											$ 700,000,000
Debt issuance costs		$ 2,200,000				$ 2,200,000
Debt instrument, term		5 years				5 years
Line of Credit
Debt Instrument
Repayments of debt	62,500,000		$ 100,000,000.0
Long-term debt, gross	$ 200,000,000	$ 200,000,000.0				$ 200,000,000.0				100,000,000
Remaining borrowing capacity		599,900,000				599,900,000
Line of Credit \| Minimum
Debt Instrument
Commitment fee (as a percent)	0.10%
Line of Credit \| Minimum \| SOFR
Debt Instrument
Basis spread on variable rate (as a percent)	1.00%
Line of Credit \| Minimum \| Base Rate
Debt Instrument
Basis spread on variable rate (as a percent)	0.00%
Line of Credit \| Maximum
Debt Instrument
Commitment fee (as a percent)	0.175%
Line of Credit \| Maximum \| SOFR
Debt Instrument
Basis spread on variable rate (as a percent)	1.75%
Line of Credit \| Maximum \| Base Rate
Debt Instrument
Basis spread on variable rate (as a percent)	0.75%
Senior Notes \| Euro Senior Notes, Series A and B
Debt Instrument
Face amount of debt \| €																		€ 212,000,000
Number of series \| series																	2	2
Senior Notes \| Euro Senior Notes, Series A due 2023
Debt Instrument
Repayments of debt \| €								€ 117,000,000
Face amount of debt \| €																		€ 117,000,000
Stated interest rate (as a percent)																	1.14%	1.14%
Senior Notes \| Euro Senior Notes, Series B due 2028
Debt Instrument
Long-term debt, gross		107,982,000				107,982,000				111,977,000
Face amount of debt \| €																		€ 95,000,000
Stated interest rate (as a percent)																	1.83%	1.83%
Senior Notes \| U.S. Senior Notes, Series A and B
Debt Instrument
Face amount of debt																	$ 125,000,000
Number of series \| series																	2	2
Senior Notes \| U.S. Senior Notes, Series A due 2022
Debt Instrument
Face amount of debt																$ 25,000,000
Stated interest rate (as a percent)																3.03%
Senior Notes \| U.S. Senior Notes, Series B due 2027
Debt Instrument
Long-term debt, gross		100,000,000				100,000,000				100,000,000
Face amount of debt																$ 100,000,000
Stated interest rate (as a percent)																3.74%
Senior Notes \| U.S. Senior Notes, Series A
Debt Instrument
Repayments of debt									$ 25,000,000
Senior Notes \| U.S. Senior Notes A and B due 2025 and 2030
Debt Instrument
Face amount of debt															$ 175,000,000
Number of series \| series															2
Senior Notes \| U.S. Senior Notes, Series A due 2025
Debt Instrument
Face amount of debt														$ 50,000,000
Stated interest rate (as a percent)														3.48%
Senior Notes \| U.S. Senior Notes, Series B due 2030
Debt Instrument
Repayments of debt					$ 50,000,000
Long-term debt, gross		$ 125,000,000				$ 125,000,000				$ 125,000,000
Face amount of debt														$ 125,000,000
Stated interest rate (as a percent)														3.78%
Senior Notes \| U.S Senior Notes, due 2032
Debt Instrument
Face amount of debt											$ 100,000,000
Stated interest rate (as a percent)											4.33%