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Segment and Geographical Area Information, Narrative (Details) - productionfacilities | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 | Mar. 31, 2016 | Dec. 31, 2016
Segment Reporting Information |  |  |
Percentage of Employees Covered by Collective Bargaining Agreements | 63.00% |  |
Percentage of Employees Covered by Collective Bargaining Agreements Expiring Within One Year | 12.00% |  |
Domestic |  |  |
Segment Reporting Information |  |  |
Number of production facilities | 11 |  |
Foreign |  |  |
Segment Reporting Information |  |  |
Number of production facilities | 1 |  |
Customer Concentration Risk | Largest Customer | Sales Revenue, Net | Fabricated Products |  |  |
Segment Reporting Information |  |  |
Concentration Risk, Percentage | 29.00% | 25.00% |
Customer Concentration Risk | Largest Customer | Accounts Receivable |  |  |
Segment Reporting Information |  |  |
Concentration Risk, Percentage | 19.00% |  | 18.00%
Customer Concentration Risk | Second Largest Customer | Sales Revenue, Net | Fabricated Products |  |  |
Segment Reporting Information |  |  |
Concentration Risk, Percentage | 10.00% | 10.00% |
Customer Concentration Risk | Second Largest Customer | Accounts Receivable |  |  |
Segment Reporting Information |  |  |
Concentration Risk, Percentage | 16.00% |  | 12.00%
Customer Concentration Risk | Second Largest Customer (number 2) | Accounts Receivable |  |  |
Segment Reporting Information |  |  |
Concentration Risk, Percentage |  |  | 12.00%

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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://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=64851502&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=73719730&loc=d3e13531-108611 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6404-108592 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13537-108611 + Details
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