Note 8 - 401(k) Retirement Benefit Plan (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Defined Contribution Plan, Employer Matching Contribution, First 3%, Percent of Match	100.00%
Defined Contribution Plan, Maximum Employee Contribution Percentage, Subject to Employer Matching Contribution	3.00%
Defined Contribution Plan, Employer Matching Contribution, Next 2%, Percent of Match	50.00%
Defined Contribution Plan, Maximum Employee Contribution Percentage, Subject to Employer 50% Matching Contribution	2.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	4.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 678	$ 600

The percentage that employers match on first 3% of contribution from employee.

No definition available.

Name:	ulbi_DefinedContributionPlanEmployerMatchingContributionFirst3PercentOfMatch
Namespace Prefix:	ulbi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The percentage that an employer will match on next 2 % of employee contributions.

No definition available.

Name:	ulbi_DefinedContributionPlanEmployerMatchingContributionNext2PercentOfMatch
Namespace Prefix:	ulbi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The maximum employee contribution percentage that is subject to employer matching 50% of contribution within a defined contribution plan.

No definition available.

Name:	ulbi_DefinedContributionPlanMaximumEmployeeContributionPercentageSubjectToEmployer50MatchingContribution
Namespace Prefix:	ulbi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The maximum employee contribution percentage that is subject to employer matching contribution within a defined contribution plan.

No definition available.

Name:	ulbi_DefinedContributionPlanMaximumEmployeeContributionPercentageSubjectToEmployerMatchingContribution
Namespace Prefix:	ulbi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Amount of discretionary contributions made by an employer to a defined contribution plan.

No definition available.

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

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration