Note 1 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Reportable Segments	3
LIFO Inventory Amount	$ 48.1	$ 43.4
Percentage of LIFO Inventory	17.50%	17.10%
Software and Software Development Costs [Member]
Property, Plant and Equipment, Useful Life	5 years
Minimum [Member]
Property, Plant and Equipment, Useful Life	2 years
Minimum [Member] \| Software and Software Development Costs [Member]
Property, Plant and Equipment, Useful Life	2 years
Maximum [Member]
Property, Plant and Equipment, Useful Life	30 years
Maximum [Member] \| Software and Software Development Costs [Member]
Property, Plant and Equipment, Useful Life	5 years
Steel Requirements [Member] \| Supplier Concentration Risk [Member] \| Three Largest Suppliers [Member]
Concentration Risk, Percentage	53.00%	54.00%	51.00%
Sales Revenue, Goods, Net [Member] \| Customer Concentration Risk [Member] \| Top 20 [Member]
Concentration Risk, Percentage	27.00%	29.00%	31.00%
Sales Revenue, Goods, Net [Member] \| Customer Concentration Risk [Member] \| Largest Customer [Member]
Concentration Risk, Percentage	4.00%	4.00%	6.00%
Sales Revenue, Goods, Net [Member] \| Customer Concentration Risk [Member] \| Industrial Machinery and Equipment Manufacturers and Fabricators [Member]
Concentration Risk, Percentage	51.00%	51.00%	49.00%
Sales Revenue, Goods, Net [Member] \| Product Concentration Risk [Member] \| Engineered Products [Member]
Concentration Risk, Percentage	1.90%	1.70%	1.80%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Paragraph 21
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766

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