Letters of credit, available borrowing capacity.

No definition available.

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

- Definition

Letters of Credit Facility, Amount Drawn

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Details

Name:	lfus_Note7DebtDetailsLineItems
Namespace Prefix:	lfus_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of credit lines assumed after acquisition.

+ References

No definition available.

+ Details

Name:	lfus_NumberofCreditLinesAssumedAfterAcquisition
Namespace Prefix:	lfus_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Credit Lines Assumed After Acquisition That Expired During Period

+ References

No definition available.

+ Details

Name:	lfus_NumberofCreditLinesAssumedAfterAcquisitionThatExpiredDuringPeriod
Namespace Prefix:	lfus_
Data Type:	xbrli:integerItemType
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 amount of cash paid for interest during the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585

+ Details

Name:	us-gaap_InterestPaid
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

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

- Definition

Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

+ 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

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

- Definition

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

+ References

No definition available.

+ Details

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

Note 7 - Debt (Details)	1 Months Ended	12 Months Ended			1 Months Ended		12 Months Ended		1 Months Ended	3 Months Ended
Note 7 - Debt (Details)	Mar. 30, 2013 USD ($)	Dec. 28, 2013 USD ($)	Dec. 29, 2012 USD ($)	Dec. 31, 2011 USD ($)	Jan. 30, 2014 Subsequent Event [Member] J.P. Morgan Securities LLC [Member] Unsecured Revolving Credit Facility [Member] USD ($)	Jan. 29, 2014 Subsequent Event [Member] J.P. Morgan Securities LLC [Member] Unsecured Revolving Credit Facility [Member] USD ($)	Dec. 28, 2013 J.P. Morgan Securities LLC [Member] Unsecured Revolving Credit Facility [Member] USD ($)	Mar. 30, 2013 J.P. Morgan Securities LLC [Member] Unsecured Revolving Credit Facility [Member] USD ($)	Mar. 30, 2013 J.P. Morgan Securities LLC [Member] USD ($)	Sep. 28, 2013 Hamlin, Inc. [Member]	Dec. 28, 2013 Hamlin, Inc. [Member] USD ($)	Dec. 28, 2013 Hamlin, Inc. [Member] CNY	Jun. 29, 2013 Hamlin, Inc. [Member] USD ($)	Jun. 29, 2013 Hamlin, Inc. [Member] CNY	Jun. 29, 2013 Hamlin, Inc. [Member] GBP (£)
Note 7 - 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		98,750,000							100,000,000
Line of Credit Facility, Expiration Period									5 years
Line of Credit Facility, Remaining Borrowing Capacity							103,400,000
Debt Instrument, Basis Spread on Variable Rate							1.25%
Line of Credit Facility, Interest Rate at Period End							1.42%
Debt Issuance Cost	800,000				100,000
Line of Credit Facility, Increase in Maximum Borrowing Capacity					50,000,000
Number of Credit Lines Assumed After Acquisition													3	3	3
Line of Credit Facility, Current Borrowing Capacity											3,300,000	20,000,000	6,600,000	41,000,000
Number of Credit Lines Assumed After Acquisition That Expired During Period										2
Other Commitment													2,700,000		1,800,000
Letters of Credit Outstanding, Amount		800,000	800,000
Letters of Credit, Available Borrowing Capacity				2,300,000
Letters of Credit Facility, Amount Drawn		0
Interest Paid		$ 2,900,000	$ 1,700,000	$ 1,700,000