XML 100 R81.htm IDEA: XBRL DOCUMENT
v3.20.4

Benefit Plans - Allocation of Plan Assets (Details) | Dec. 26, 2020 | Dec. 28, 2019
--- | --- | ---
Defined Benefit Plan Disclosure |  |
Asset Allocation | 100.00% | 100.00%
Cash and cash equivalents |  |
Defined Benefit Plan Disclosure |  |
Asset Allocation | 7.00% | 1.00%
Equity securities |  |
Defined Benefit Plan Disclosure |  |
Asset Allocation | 9.00% | 27.00%
Fixed income securities |  |
Defined Benefit Plan Disclosure |  |
Asset Allocation | 31.00% | 72.00%
Bulk annuity contract |  |
Defined Benefit Plan Disclosure |  |
Asset Allocation | 53.00% | 0.00%

X
- 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. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=lfus_BulkAnnuityContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |