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PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Details) $ in Thousands | 3 Months Ended | 9 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 30, 2016 USD ($) | Sep. 30, 2015 USD ($) | Sep. 30, 2016 USD ($) plan | Sep. 30, 2015 USD ($) | Jun. 30, 2016 | Mar. 31, 2016 | Jan. 01, 2016 | Dec. 31, 2015
Components of net periodic benefit cost |  |  |  |  |  |  |  |
Pension settlement expense | $ 800 | $ 800 | $ 2,267 | $ 2,478 |  |  |  |
Pension settlement expense, net of tax | 490 | 466 | 1,385 | 1,514 |  |  |  |
Freight Transportation (ABF Freight) |  |  |  |  |  |  |  |
Components of net periodic benefit cost |  |  |  |  |  |  |  |
Pension settlement expense | 600 | 600 | $ 1,700 | 1,900 |  |  |  |
Multiemployer pension plans | Freight Transportation (ABF Freight) |  |  |  |  |  |  |  |
Multiemployer Plans |  |  |  |  |  |  |  |
Number of multiemployer plans to which ABF Freight currently contributes | plan |  |  | 25 |  |  |  |  |
Maximum projected time to insolvency for plans in "critical and declining" status |  |  | 14 years |  |  |  |  |
Maximum projected time to insolvency for plans in "critical and declining" status if additional criteria apply |  |  | 19 years |  |  |  |  |
Threshold ratio of inactive to active participants for greater insolvency period to determine "critical and declining" status |  |  | 2 |  |  |  |  |
Threshold funded percentage for greater insolvency period to determine "critical and declining" status |  |  | 80.00% |  |  |  |  |
Multiemployer pension plans | Central States Pension Plan |  |  |  |  |  |  |  |
Multiemployer Plans |  |  |  |  |  |  |  |
Maximum projected time to insolvency without legislative action |  |  | 10 years |  |  |  |  |
Multiemployer pension plans | Central States Pension Plan | Freight Transportation (ABF Freight) |  |  |  |  |  |  |  |
Multiemployer Plans |  |  |  |  |  |  |  |
Approximate proportion of multiemployer pension plan contributions (as a percent) |  |  | 50.00% |  |  |  |  |
Actuarially certified projected funded percentage of multiemployer pension plan |  |  |  |  |  |  | 46.90% |
Multiemployer pension plans | 707 Pension Fund | Freight Transportation (ABF Freight) |  |  |  |  |  |  |  |
Multiemployer Plans |  |  |  |  |  |  |  |
Approximate proportion of multiemployer pension plan contributions (as a percent) |  |  | 1.00% |  |  |  |  |
Nonunion Defined Benefit Pension Plan |  |  |  |  |  |  |  |
Components of net periodic benefit cost |  |  |  |  |  |  |  |
Interest cost | 1,057 | 1,356 | $ 3,520 | 3,899 |  |  |  |
Expected return on plan assets | (2,242) | (2,297) | (6,346) | (7,058) |  |  |  |
Pension settlement expense | 803 | 762 | 2,267 | 2,478 |  |  |  |
Amortization of net actuarial loss | 1,106 | 640 | 3,123 | 2,276 |  |  |  |
Net periodic benefit cost | 724 | 461 | 2,564 | 1,595 |  |  |  |
Pension settlement expense, net of tax | 500 | 500 | 1,400 | 1,500 |  |  |  |
Lump-sum distributions | 4,300 | 4,100 | 11,600 | 16,600 |  |  |  |
Change in projected benefit obligation |  |  |  |  |  |  |  |
Benefit obligations at beginning of period |  |  | 159,607 |  |  |  |  |
Interest cost | 1,057 | 1,356 | 3,520 | 3,899 |  |  |  |
Actuarial loss |  |  | 10,068 |  |  |  |  |
Benefits paid |  |  | (11,860) |  |  |  |  |
Benefit obligations at end of period | 161,335 |  | 161,335 |  |  |  |  |
Change in plan assets |  |  |  |  |  |  |  |
Fair value of plan assets at beginning of period |  |  | 136,917 |  |  |  |  |
Actual return on plan assets |  |  | 9,637 |  |  |  |  |
Employer contributions |  |  | 13,400 |  |  |  |  |
Benefits paid |  |  | (11,860) |  |  |  |  |
Fair value of plan assets at end of period | 148,094 |  | 148,094 |  |  |  |  |
Funded status | (13,241) |  | (13,241) |  |  |  |  |
Accumulated benefit obligation | $ 161,335 |  | $ 161,335 |  |  |  |  |
Discount rate (as a percent) | 2.70% |  | 2.70% |  | 2.70% | 3.00% |  | 3.50%
Adjusted funding target attainment percentage |  |  |  |  |  |  | 107.80% |
Supplemental Benefit Plan |  |  |  |  |  |  |  |
Components of net periodic benefit cost |  |  |  |  |  |  |  |
Interest cost | $ 32 | 31 | $ 97 | 92 |  |  |  |
Amortization of net actuarial loss | 38 | 40 | 114 | 120 |  |  |  |
Net periodic benefit cost | 70 | 71 | 211 | 212 |  |  |  |
Change in projected benefit obligation |  |  |  |  |  |  |  |
Interest cost | 32 | 31 | 97 | 92 |  |  |  |
Postretirement Health Benefit Plan |  |  |  |  |  |  |  |
Components of net periodic benefit cost |  |  |  |  |  |  |  |
Service cost | 107 | 101 | 321 | 304 |  |  |  |
Interest cost | 254 | 228 | 763 | 685 |  |  |  |
Amortization of prior service credit | (47) | (47) | (142) | (142) |  |  |  |
Amortization of net actuarial loss | 177 | 213 | 529 | 639 |  |  |  |
Net periodic benefit cost | 491 | 495 | 1,471 | 1,486 |  |  |  |
Change in projected benefit obligation |  |  |  |  |  |  |  |
Interest cost | $ 254 | $ 228 | $ 763 | $ 685 |  |  |  |

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- Definition The threshold funded percentage of plans, below which a higher maximum period for insolvency is used to determine "critical and declining" status. + References No definition available. + Details
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- Definition The threshold ratio of inactive participants to active participants, above which a higher maximum period for insolvency is used to determine "critical and declining" status. + References No definition available. + Details
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- Definition The maximum period within which a plan in "critical and declining" status is expected to become insolvent, unless additional criteria relating to ratio of inactive to active participants or funded percentage are applicable. + References No definition available. + Details
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- Definition Net of tax amount of the gain (loss) adjustment to other comprehensive income (loss) resulting from the settlement of the entity's defined benefit pension and other postretirement plans. + References No definition available. + Details
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- Definition For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Accumulated Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6503844 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Actual Return on Plan Assets (Component of Net Periodic Postretirement Benefit Cost) -URI http://asc.fasb.org/extlink&oid=6504192 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Actual Return on Plan Assets (Component of Net Periodic Pension Cost) -URI http://asc.fasb.org/extlink&oid=6504226 + Details
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- Definition Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Gain or Loss -URI http://asc.fasb.org/extlink&oid=49168827 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The amount of gains or losses recognized in net periodic benefit cost. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Prior Service Cost -URI http://asc.fasb.org/extlink&oid=49177896 + Details
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- Definition The interest rate used to adjust for the time value of money for the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition 1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Projected Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6522206 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Accumulated Postretirement Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6503904 + Details
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- Definition The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Benefits -URI http://asc.fasb.org/extlink&oid=49170737 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(6) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Postretirement Benefits -URI http://asc.fasb.org/extlink&oid=6521376 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(5) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Amount of contributions made by the employer to defined benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(ii) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 35 -Paragraph 123 -Subparagraph B -URI http://asc.fasb.org/extlink&oid=64937487&loc=d3e36068-114959 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 35 -Paragraph 63 -Subparagraph B -URI http://asc.fasb.org/extlink&oid=64937038&loc=d3e12551-114930 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(iv)(01) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Expected Return on Plan Assets -URI http://asc.fasb.org/extlink&oid=6512171 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 35 -Paragraph 50 -URI http://asc.fasb.org/extlink&oid=64937038&loc=d3e12355-114930 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Plan Assets -URI http://asc.fasb.org/extlink&oid=6749337 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Plan Assets -URI http://asc.fasb.org/extlink&oid=6520858 + Details
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- Definition The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64852052&loc=d3e1703-114919 + Details
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- Definition The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Amount of net gain (loss) recognized in net periodic benefit cost as a result of an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include, but are not limited to, lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contracts to cover vested benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 15 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(7) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Service Cost (Component of Net Periodic Pension Cost) -URI http://asc.fasb.org/extlink&oid=6525008 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- References No definition available. + Details
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