Note 15 - Segment Reporting - Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Revenues from external customers									$ 198,496	$ 178,220
Revenue from Contract with Customer, Including Assessed Tax	$ 40,322	$ 54,614	$ 54,926	$ 48,634	$ 49,253	$ 46,138	$ 41,169	$ 41,660	198,496	178,220
Operating profit (loss)	(1,818)	$ (475)	$ 1,035	$ 1,680	(1,399)	$ (258)	$ (206)	$ (494)	422	(2,357)
Depreciation and amortization									6,279	7,497
Capital expenditures									1,547	1,844
Total assets	119,682				122,866				119,682	122,866
Consolidation, Eliminations [Member]
Revenues from external customers
Revenue from Contract with Customer, Including Assessed Tax									(137)	(7)
Operating profit (loss)									(8)
Depreciation and amortization
Capital expenditures
Total assets	(194,747)				(214,110)				(194,747)	(214,110)
Intersegment Eliminations [Member]
Revenue from Contract with Customer, Including Assessed Tax
Heavy Fabrications [Member]
Total assets	40,438				41,432				40,438	41,432
Heavy Fabrications [Member] | Operating Segments [Member]
Revenues from external customers									155,096	128,686
Revenue from Contract with Customer, Including Assessed Tax									155,198	128,686
Operating profit (loss)									10,385	1,861
Depreciation and amortization									3,736	3,976
Capital expenditures									1,049	992
Heavy Fabrications [Member] | Intersegment Eliminations [Member]
Revenue from Contract with Customer, Including Assessed Tax									102
Gearing [Member]
Total assets	43,319				47,022				43,319	47,022
Gearing [Member] | Operating Segments [Member]
Revenues from external customers									25,104	34,877
Revenue from Contract with Customer, Including Assessed Tax									25,136	34,877
Operating profit (loss)									(3,883)	3,237
Depreciation and amortization									1,961	1,981
Capital expenditures									283	769
Gearing [Member] | Intersegment Eliminations [Member]
Revenue from Contract with Customer, Including Assessed Tax									32
Industrial Solutions [Member]
Total assets	10,244				8,893				10,244	8,893
Industrial Solutions [Member] | Operating Segments [Member]
Revenues from external customers									18,296	14,657
Revenue from Contract with Customer, Including Assessed Tax									18,299	14,664
Operating profit (loss)									881	(1,059)
Depreciation and amortization									430	1,362
Capital expenditures									159	52
Industrial Solutions [Member] | Intersegment Eliminations [Member]
Revenue from Contract with Customer, Including Assessed Tax									3	7
Corporate Segment [Member]
Total assets	$ 220,428				$ 239,629				220,428	239,629
Corporate Segment [Member] | Operating Segments [Member]
Revenues from external customers
Revenue from Contract with Customer, Including Assessed Tax
Operating profit (loss)									(6,953)	(6,396)
Depreciation and amortization									152	178
Capital expenditures									56	31
Corporate Segment [Member] | Intersegment Eliminations [Member]
Revenue from Contract with Customer, Including Assessed Tax