The increase of the maximum borrowing capacity of the company's revolving line of credit.

No definition available.

Name:	lfus_LineofCreditFacilityIncreaseinMaximumBorrowingCapacity
Namespace Prefix:	lfus_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	lfus_Note6DebtDetailsLineItems
Namespace Prefix:	lfus_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of debt issuance costs (for example, but not limited to, legal, accounting, broker, and regulatory fees).

+ References

No definition available.

+ Details

Name:	us-gaap_DebtIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The effective interest rate at the end of the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of loans from a bank with maturities initially due after one year or beyond the normal operating cycle if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Note 6 - Debt (Details) (USD $)			3 Months Ended	1 Months Ended
Note 6 - Debt (Details) (USD $)	Mar. 29, 2014	Dec. 28, 2013	Mar. 29, 2014 J.P. Morgan Securities LLC [Member] Base Rate [Member] Unsecured Revolving Credit Facility [Member]	Jan. 30, 2014 J.P. Morgan Securities LLC [Member] Unsecured Revolving Credit Facility [Member]	Mar. 29, 2014 J.P. Morgan Securities LLC [Member] Unsecured Revolving Credit Facility [Member]	Jan. 29, 2014 J.P. Morgan Securities LLC [Member] Unsecured Revolving Credit Facility [Member]	May 31, 2013 J.P. Morgan Securities LLC [Member] Unsecured Revolving Credit Facility [Member]	May 31, 2013 J.P. Morgan Securities LLC [Member]
Note 6 - Debt (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 275,000,000		$ 225,000,000	$ 225,000,000	$ 325,000,000
Loans Payable to Bank	97,500,000	98,750,000						100,000,000
Line of Credit Facility, Increase in Maximum Borrowing Capacity				50,000,000
Debt Issuance Cost				100,000
Line of Credit Facility, Remaining Borrowing Capacity					$ 86,400,000
Debt Instrument, Basis Spread on Variable Rate			1.25%
Line of Credit Facility, Interest Rate at Period End					1.40%