Note 2 - Acquisition (Details Textual) - USD ($) $ in Thousands		5 Months Ended	9 Months Ended
May 01, 2019	Sep. 29, 2019	Sep. 30, 2020	Sep. 29, 2019
Payments to Acquire Businesses, Net of Cash Acquired, Total			$ (0)	$ 25,248
Share-based Payment Arrangement, Noncash Expense, Total			756	$ 519
Southwest Electronic Energy Corporation [Member]
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Payments to Acquire Businesses, Net of Cash Acquired, Total	$ 26,190
Cash Acquired from Acquisition	$ 942
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		$ 11,993	13,382
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual		740	858
Business Combination, Interest Expense, Financing		289	273
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles		101	$ 182
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory		264
Business Combination, Acquisition Related Costs		165
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment		55
Share-based Payment Arrangement, Noncash Expense, Total		$ 49

The amount of interest expense related to financing for a business combination.

No definition available.

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Namespace Prefix:	ulbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e1043-128460

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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Balance Type:	credit
Period Type:	duration

- Definition

This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)
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- Definition

This element represents the amount of any measurement period adjustment (as defined) realized during the reporting period to intangibles acquired in connection with a business combination for which the initial accounting was incomplete.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 4A
-Subparagraph (c)
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- Definition

This element represents the amount of any measurement period adjustment (as defined) realized during the reporting period to inventory acquired in connection with a business combination for which the initial accounting was incomplete.

+ References

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- Definition

This element represents the amount of any measurement period adjustment (as defined) realized during the reporting period to property, plant, and equipment acquired in connection with a business combination for which the initial accounting was incomplete.

+ References

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- Definition

The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
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- Definition

The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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-Paragraph 13
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- Definition

Amount of noncash expense for share-based payment arrangement.

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-Name Accounting Standards Codification
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- Details

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