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Commitments and Contingencies - Collective Bargaining and Union Agreements (Details) (Employee Concentration Risk)
 12 Months Ended
Dec. 31, 2014
Workforce Subject to Collective Bargaining Arrangements or Member of Unions or Councils
  
Concentration Risk [Line Items]  
Concentration risk, percentage 69.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= xrm_WorkforceSubjectToCollectiveBargainingArrangementsOrMemberOfUnionsOrCouncilsMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_LaborForceConcentrationRiskMember
Workforce Subject to Collective Bargaining Arrangements
  
Concentration Risk [Line Items]  
Concentration risk, percentage 12.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_LaborForceConcentrationRiskMember
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year
  
Concentration Risk [Line Items]  
Concentration risk, percentage 9.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsExpiringWithinOneYearMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_LaborForceConcentrationRiskMember