Represents number of monthly payments for debt instrument.

No definition available.

Name:	ulbi_DebtInstrumentNumberOfMonthlyPayment
Namespace Prefix:	ulbi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents line of credit facility maximum borrowing capacity contingent on bank approval.

+ References

No definition available.

+ Details

Name:	ulbi_LineOfCreditFacilityMaximumBorrowingCapacityContingentOnBankApproval
Namespace Prefix:	ulbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents information related to consolidated senior leverage ratio.

+ References

No definition available.

+ Details

Name:	ulbi_MaximumConsolidatedSeniorLeverageRatio
Namespace Prefix:	ulbi_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

The minimum fixed charge coverage ratio required for certain debt covenants.

+ References

No definition available.

+ Details

Name:	ulbi_MinimumFixedChargeCoverageRatio
Namespace Prefix:	ulbi_
Data Type:	xbrli:pureItemType
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:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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+ Details

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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-Name Accounting Standards Codification
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+ Details

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

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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+ Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=ulbi_TermLoanFacilityMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

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Note 2 - Debt (Details Textual) $ in Thousands		9 Months Ended	12 Months Ended
Note 2 - Debt (Details Textual) $ in Thousands	May 01, 2019 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	May 31, 2019
Term Loan Facility [Member]
Debt Instrument, Number of Monthly Payment				60
Amended Credit Agreement [Member]
Debt Issuance Costs, Gross		$ 35
Repayments of Long-term Debt, Total		0	$ 4,200
Amended Credit Agreement [Member] \| Revolving Credit Facility [Member]
Long-term Line of Credit, Total		0
Minimum Fixed Charge Coverage Ratio	1.15
Maximum Consolidated Senior Leverage Ratio	2.5
Amended Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Minimum [Member]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.10%
Amended Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Maximum [Member]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.20%
Amended Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Fed Funds Effective Rate Overnight Index Swap Rate [Member]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Amended Credit Agreement [Member] \| Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Amended Credit Agreement [Member] \| Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	1.85%
Amended Credit Agreement [Member] \| Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	2.15%
Amended Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Base Rate [Member] \| Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	0.00%
Amended Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Base Rate [Member] \| Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	(0.50%)
Term Loan Facility [Member] \| Revolving Credit Facility [Member]
Secured Debt, Total		$ 288
KeyBank [Member] \| Amended Credit Agreement [Member] \| Term Loan Facility [Member]
Debt Instrument, Term (Year)	5 years
Debt Instrument, Face Amount	$ 8,000
KeyBank [Member] \| Amended Credit Agreement [Member] \| Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	30,000
Line Of Credit Facility Maximum Borrowing Capacity Contingent On Bank Approval	$ 50,000