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EMPLOYEE BENEFIT PLANS (Details 3) (Nonunion Defined Benefit Pension Plan)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Nonunion Defined Benefit Pension, Supplemental Benefit, and Postretirement Health Benefit Plans    
Expected return on plan assets expected to be utilized in determining pension plan expenses for next fiscal year (as a percent) 6.50%arcb_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssetsForNextFiscalYear  
Period over which the possibility of experiencing a substantial loss is limited by adequate diversification under the long-term asset allocation policy 1 year  
Target allocations, acceptable ranges, and actual asset allocations    
Target allocation (as a percent) 100.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations  
Weighted-Average Allocation (as a percent) 100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations 100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Maximum performance period of investment fund used to compare investment performance 3 years  
Minimum performance period of total fund used to compare investment performance 5 years  
Minimum
    
Target allocations, acceptable ranges, and actual asset allocations    
Performance period of recognized market indices used to compare investment performance 3 years  
Maximum
    
Target allocations, acceptable ranges, and actual asset allocations    
Performance period of recognized market indices used to compare investment performance 5 years  
Large Cap U.S. Equity
    
Target allocations, acceptable ranges, and actual asset allocations    
Target allocation (as a percent) 15.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_LargeCapUSEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, minimum (as a percent) 10.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_LargeCapUSEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, maximum (as a percent) 25.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_LargeCapUSEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Weighted-Average Allocation (as a percent) 18.90%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_LargeCapUSEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		 23.80%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_LargeCapUSEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Mid Cap U.S. Equity
    
Target allocations, acceptable ranges, and actual asset allocations    
Target allocation (as a percent) 10.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_MidCapEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, minimum (as a percent) 8.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_MidCapEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, maximum (as a percent) 12.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_MidCapEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Weighted-Average Allocation (as a percent) 12.10%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_MidCapEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		 10.70%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_MidCapEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Small Cap U.S. Equity
    
Target allocations, acceptable ranges, and actual asset allocations    
Target allocation (as a percent) 10.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_SmallCapUSEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, minimum (as a percent) 8.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_SmallCapUSEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, maximum (as a percent) 12.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_SmallCapUSEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Weighted-Average Allocation (as a percent) 11.30%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_SmallCapUSEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		 10.50%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_SmallCapUSEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
International Equity
    
Target allocations, acceptable ranges, and actual asset allocations    
Target allocation (as a percent) 15.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_InternationalEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, minimum (as a percent) 11.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_InternationalEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, maximum (as a percent) 19.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_InternationalEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Weighted-Average Allocation (as a percent) 15.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_InternationalEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		 12.50%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_InternationalEquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Debt Instruments
    
Target allocations, acceptable ranges, and actual asset allocations    
Target allocation (as a percent) 30.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, minimum (as a percent) 20.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, maximum (as a percent) 35.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Weighted-Average Allocation (as a percent) 20.40%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		 17.60%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Floating Rate Loan Fund
    
Target allocations, acceptable ranges, and actual asset allocations    
Target allocation (as a percent) 10.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_FloatingRateLoanFundMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, minimum (as a percent) 3.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_FloatingRateLoanFundMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, maximum (as a percent) 15.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_FloatingRateLoanFundMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Weighted-Average Allocation (as a percent) 10.20%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_FloatingRateLoanFundMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		 3.60%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= arcb_FloatingRateLoanFundMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Cash and Cash Equivalents
    
Target allocations, acceptable ranges, and actual asset allocations    
Target allocation (as a percent) 10.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_CashAndCashEquivalentsMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, minimum (as a percent) 0.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_CashAndCashEquivalentsMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Acceptable Range, maximum (as a percent) 15.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_CashAndCashEquivalentsMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		  
Weighted-Average Allocation (as a percent) 12.10%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_CashAndCashEquivalentsMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember		 21.30%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_CashAndCashEquivalentsMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Actively managed portfolio of short-term debt instruments | Minimum
    
Target allocations, acceptable ranges, and actual asset allocations    
Maturity period of investments 1 year  
Actively managed portfolio of short-term debt instruments | Maximum
    
Target allocations, acceptable ranges, and actual asset allocations    
Maturity period of investments 5 years  
Actively managed portfolio of short-duration debt instruments | Minimum
    
Target allocations, acceptable ranges, and actual asset allocations    
Maturity period of investments 1 year  
Actively managed portfolio of short-duration debt instruments | Maximum
    
Target allocations, acceptable ranges, and actual asset allocations    
Maturity period of investments 3 years