Note 11 - Business Segment Information - Segment Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue	$ 107,712	$ 106,795
Segment contribution	5,701	7,368
Other income	(1,322)	597
Income tax provision (benefit)	1,692	1,457
Non-controlling interest	99	109
Net income attributable to Ultralife	5,232	5,205
Total assets	137,701	144,557
Capital expenditures	3,101	6,281
Goodwill	27,018	26,753	$ 20,109
Depreciation and amortization of intangible assets	2,935	2,745
Stock-based compensation	943	753
Battery & Energy Products Segment [Member]
Revenue	91,907	83,996
Segment contribution	23,400	22,813
Total assets	85,112	79,413
Capital expenditures	3,031	5,805
Goodwill	15,525	15,260	8,616
Depreciation and amortization of intangible assets	2,269	2,104
Stock-based compensation	446	355
Communications Systems Segment [Member]
Revenue	15,805	22,799
Segment contribution	5,759	8,352
Total assets	26,425	40,458
Capital expenditures	0	44
Goodwill	11,493	11,493	$ 11,493
Depreciation and amortization of intangible assets	342	364
Stock-based compensation	155	119
Corporate Segment [Member]
Revenue	0	0
Segment contribution	(23,458)	(23,797)
Other income	(1,322)	597
Income tax provision (benefit)	1,692	1,457
Non-controlling interest	99	109
Total assets	26,164	24,686
Capital expenditures	70	432
Goodwill	0	0
Depreciation and amortization of intangible assets	324	277
Stock-based compensation	$ 342	$ 279