Represents the percentage of price paid per share for equity securities.

No definition available.

Name:	cui_ConvertibleNotesAutomaticConversionPricePercentageOfPricePaidPerShareForEquitySecuritiesByInvestors
Namespace Prefix:	cui_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the interest rate on convertible note receivable.

+ References

No definition available.

+ Details

Name:	cui_InterestRateOnConvertibleNoteReceivable
Namespace Prefix:	cui_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The interest rate on a note receivable

+ References

No definition available.

+ Details

Name:	cui_InterestRateOnNoteReceivable
Namespace Prefix:	cui_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the minimum proceeds from sale of VPS equity securities for principal and accrued interest of convertible note receivable to automatically convert into VPS shares.

+ References

No definition available.

+ Details

Name:	cui_MinimumProceedsFromSaleOfVpsEquitySecuritiesForPrincipalAndAccruedInterestOfConvertibleNoteReceivableToAutomaticallyConvertIntoVpsShares
Namespace Prefix:	cui_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A valuation allowance relating to a written agreement to receive money (at a specified future date(s) within one year from the reporting date (or the normal operating cycle, whichever is longer), consisting of principal as well as any accrued interest) for the portion that is expected to be uncollectible.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.4)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

+ Details

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

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

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

- Definition

Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(b))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

+ Details

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

- Definition

For an unclassified balance sheet, amounts due from parties associated with the reporting entity as evidenced by a written promise to pay.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.3)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

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

- Definition

The cash outflow to acquire an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among myriad other features and characteristics.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

+ Details

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

- Definition

The cash inflow associated with principal collections from a borrowing supported by a written promise to pay an obligation.

+ 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 (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585

+ Details

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

- Details

Name:	srt_CounterpartyNameAxis=cui_VirtualPowerSystemsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=cui_TestProductsInternationalIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 7 - Investments (Details Textual) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended
	Jul. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Investment Income, Interest		$ 4	$ 5		$ 13	$ 13
Proceeds from Collection of Notes Receivable						19
Payments to Acquire Notes Receivable		500			500
Virtual Power Systems [Member]
Payments to Acquire Notes Receivable	$ 500
Interest Rate on Convertible Note Receivable	2.00%
Minimum Proceeds from Sale of VPS Equity Securities for Principal and Accrued Interest of Convertible Note Receivable to Automatically Convert Into VPS Shares	$ 3,000
Convertible Notes, Automatic Conversion Price, Percentage of Price Paid Per Share for Equity Securities by Investors	80.00%
Test Products International Inc. [Member]
Equity Method Investment, Ownership Percentage				8.50%
Notes Receivable, Related Parties		300		$ 400	300		$ 300
Interest Rate on Note Receivable				5.00%
Allowance for Notes, Loans and Financing Receivable, Current		$ 0			$ 0