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v3.19.3.a.u2

LEASES (Lease terms) (Details) - Maximum | 12 Months Ended
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Dec. 31, 2019
Operating leases |
Remaining lease term | 10 years
Operating lease, renewal term | 5 years
Option to terminate lease, period | 2 years

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- Definition Period over which entity, as a lessee, has an option to terminate operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | arcb_LesseeOperatingLeaseOptionToTerminatePeriod
Namespace Prefix: | arcb_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition The remaining term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | arcb_LesseeOperatingLeaseRemainingTermOfContract
Namespace Prefix: | arcb_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_LesseeOperatingLeaseDescriptionAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
Name: | us-gaap_LesseeOperatingLeaseRenewalTerm
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |