SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Inventory Reserves (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Inventory [Line Items]
Inventory reserves, beginning of year	[1]	$ 483
Inventory reserves, end of year		774	$ 483	[1]
Inventory Valuation Reserve [Member]
Inventory [Line Items]
Inventory reserves, beginning of year		483	394		$ 550
Charge to costs and expenses		312	94		(148)
Deductions		(21)	(5)		(8)
Inventory reserves, end of year		$ 774	$ 483		$ 394

[1] At December 31, 2015, CUI-Canada inventory reserves of $97 thousand were reclassified from raw materials to inventory reserves and $246 thousand of prepaid expenses at CUI Inc. were reclassified to raw materials inventory.