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Business, Product and Geographical Area Information and Concentration of Risk - Narrative (Details) | 12 Months Ended
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Dec. 31, 2018 productionfacilities customer | Dec. 31, 2017 customer | Dec. 31, 2016 customer
Segment Reporting Information |  |  |
Percentage of Employees Covered by Collective Bargaining Agreements | 62.00% |  |
Percentage of Employees Covered by Collective Bargaining Agreements Expiring Within One Year | 0.00% |  |
United States |  |  |
Segment Reporting Information |  |  |
Number of production facilities | 12 |  |
Canada |  |  |
Segment Reporting Information |  |  |
Number of production facilities | 1 |  |
Customer Concentration Risk [Member] | Net sales | Largest Customer [Member] | Fabricated Products |  |  |
Segment Reporting Information |  |  |
Concentration risk, percentage | 25.00% | 27.00% | 26.00%
Number of Customers | customer | 1 | 1 | 1
Customer Concentration Risk [Member] | Net sales | Second Largest Customer [Member] | Fabricated Products |  |  |
Segment Reporting Information |  |  |
Concentration risk, percentage | 15.00% | 12.00% | 10.00%
Customer Concentration Risk [Member] | Trade receivables | Largest Customer [Member] |  |  |
Segment Reporting Information |  |  |
Concentration risk, percentage | 31.00% | 22.00% |
Customer Concentration Risk [Member] | Trade receivables | Second Largest Customer [Member] |  |  |
Segment Reporting Information |  |  |
Concentration risk, percentage | 11.00% | 14.00% |

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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13531-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13537-108611 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592 + Details
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