Note 16 - Overdraft Facility and Working Capital Line of Credit - Revolving Line of Credit (Details) £ in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)		Sep. 30, 2018 GBP (£)
General Intangibles [Member] | CUI, Inc [Member]
Collateral, amount	$ 8,690
Accounts Receivable [Member] | CUI, Inc [Member]
Collateral, amount	8,284
Inventory [Member] | CUI, Inc [Member]
Collateral, amount	11,168
Equipment [Member] | CUI, Inc [Member]
Collateral, amount	$ 1,690
Multi-currency Variable Rate Overdraft Facility [Member] | Wells Fargo Bank N.A [Member]
Line of credit facility, maximum borrowing capacity | £			£ 1,278
Line of credit facility, expiration date	Oct. 05, 2021
Line of credit facility, interest rate	2.50%		2.50%
Line of credit facility, expiration date	Oct. 05, 2021
Multi-currency Variable Rate Overdraft Facility [Member] | Wells Fargo Bank N.A [Member] | Base Rate [Member]
Line of credit facility, variable interest rate	2.25%
Revolving Credit Facility [Member] | Wells Fargo Bank N.A [Member] | CUI, Inc [Member]
Line of credit facility, maximum borrowing capacity	$ 3,300
Line of credit facility	700
Revolving Credit Facility [Member] | Wells Fargo Bank [Member]
Line of credit facility, maximum borrowing capacity	$ 4,000
Line of credit facility, expiration date	Jun. 01, 2019
Line of credit facility, interest rate	2.25%		2.25%
Line of credit facility	$ 657	[1]
Line of credit facility, expiration date	Jun. 01, 2019
Revolving Credit Facility [Member] | Wells Fargo Bank [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of credit facility, variable interest rate	2.25%

[1] As a result of the Company’s cash management system, checks issued but not presented to the bank for payment may create negative book cash balances. When those checks are presented for payment if there isn't sufficient cash in the bank account, the checks would be honored by the bank with a corresponding increase to CUI's draw on its line of credit. There were no negative book cash balances included in the balance on the line of credit as of September 30, 2018.