Note 11 - Accumulated Other Comprehensive Income (Loss) (AOCI) (Details Textual) - USD ($)	Sep. 26, 2015	Dec. 27, 2014
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	$ 3,115,000	$ 12,587,000
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Tax	$ 0	$ 0

The amount of tax accumulated for the total of net gain (loss), prior service cost (credit), and transition assets (obligations), as well as minimum pension liability if still remaining, included in accumulated other comprehensive income associated with a defined benefit pension or other postretirement plan(s) because they have yet to be recognized as components of net periodic benefit cost.

No definition available.

Name:	lfus_AccumulatedOtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax
Namespace Prefix:	lfus_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant