XML 67 R53.htm IDEA: XBRL DOCUMENT
v3.19.1

Summary of Significant Accounting Policies Concentration Risk (Details) | 12 Months Ended
--- | ---
Dec. 31, 2018 Employee Customer | Dec. 31, 2017 | Dec. 31, 2016
Sales Revenue, Total [Member] | Customer Concentration Risk [Member] |  |  |
Concentration risk: |  |  |
Number of major customers, Sales | Customer | 4 |  |
Concentration Risk, Percentage | 65.00% | 65.00% | 68.00%
Sales Revenue, Total [Member] | Geographic concentration risk | Mexico and Canada [Member] |  |  |
Concentration risk: |  |  |
Concentration Risk, Percentage | 32.00% | 36.00% | 32.00%
Accounts Receivable [Member] | Customer Concentration Risk [Member] |  |  |
Concentration risk: |  |  |
Concentration Risk, Accounts Receivable, Number of major customers | Customer | 4 |  |
Concentration Risk, Percentage | 64.00% | 74.00% |
Number of employees, geographic area | Labor force concentration risk |  |  |
Concentration risk: |  |  |
Concentration risk, number of employees | 2,190 |  |
Number of employees, geographic area | Labor force concentration risk | MEXICO |  |  |
Concentration risk: |  |  |
Concentration risk, number of employees | 1,033 |  |
Number of employees, geographic area | Labor force concentration risk | United States |  |  |
Concentration risk: |  |  |
Concentration risk, number of employees | 886 |  |
Number of employees, geographic area | Labor force concentration risk | CANADA |  |  |
Concentration risk: |  |  |
Concentration risk, number of employees | 271 |  |
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk | International Association of Machinists and Aerospace Workers |  |  |
Concentration risk: |  |  |
Concentration risk, number of employees | 372 |  |
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk | Sindicato de Jorneleros y Obreros |  |  |
Concentration risk: |  |  |
Concentration risk, number of employees | 876 |  |
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk | United Food & Commercial Workers Canada [Member] [Member] |  |  |
Concentration risk: |  |  |
Concentration risk, number of employees | 221 |  |
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk | Sindicato de trabajadores de la industria metalica y del comercio del estado de Nuevo Leon Presidente Benito Juarez Garcia C.T.M. [Member] |  |  |
Concentration risk: |  |  |
Concentration risk, number of employees | 26 |  |

X
- Definition Concentration Risk, Number of Employees + References No definition available. + Details
Name: | cmt_ConcentrationRiskNumberOfEmployees
Namespace Prefix: | cmt_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Concentration Risk, Sales, Number of Significant Customers + References No definition available. + Details
Name: | cmt_ConcentrationRiskSalesNumberofSignificantCustomers
Namespace Prefix: | cmt_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of major customers, Accounts Receivable + References No definition available. + Details
Name: | cmt_NumberofmajorcustomersAccountsReceivable
Namespace Prefix: | cmt_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ConcentrationRiskLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- 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=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 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=84177426&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=77997519&loc=d3e13537-108611 + Details
Name: | us-gaap_ConcentrationRiskPercentage1
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=cmt_SalesRevenueTotalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_GeographicConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=cmt_MexicoAndCanadaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_AccountsReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_NumberOfEmployeesGeographicAreaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_LaborForceConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_MX
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_US
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_CA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_UnionizedEmployeesConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CollectiveBargainingArrangementAxis=cmt_InternationalAssociationOfMachinistsAndAerospaceWorkersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CollectiveBargainingArrangementAxis=cmt_SindicatoDeJornelerosYObrerosMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CollectiveBargainingArrangementAxis=cmt_UnitedFoodCommercialWorkersCanadaMemberMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CollectiveBargainingArrangementAxis=cmt_SindicatodetrabajadoresdelaindustriametalicaydelcomerciodelestadodeNuevoLeonPresidenteBenitoJuarezGarciaC.T.M.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |