PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) plan	Mar. 31, 2015 USD ($)	Jan. 01, 2016	Dec. 31, 2015	Jan. 01, 2015
Components of net periodic benefit cost
Pension settlement expense	$ 900	$ 1,119
Pension settlement expense, net of tax	550	684
Freight Transportation (ABF Freight)
Components of net periodic benefit cost
Pension settlement expense	$ 700	800
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 | Freight Transportation (ABF Freight)
Multiemployer Plans
Approximate proportion of multiemployer pension plan contributions (as a percent)	50.00%
Actuarially certified funded percentage of multiemployer pension plan					46.90%
Nonunion Defined Benefit Pension Plan
Components of net periodic benefit cost
Interest cost	$ 1,305	1,320
Expected return on plan assets	(1,946)	(2,402)
Pension settlement expense	900	1,119
Amortization of net actuarial loss	955	821
Net periodic benefit cost	1,214	858
Pension settlement expense, net of tax	600	700
Lump-sum distributions	4,500	7,600
Change in projected benefit obligation
Benefit obligations at beginning of period	159,607
Interest cost	1,305	1,320
Actuarial loss	5,723
Benefits paid	(4,590)
Benefit obligations at end of period	162,045
Change in plan assets
Fair value of plan assets at beginning of period	136,917
Actual return on plan assets	1,935
Benefits paid	(4,590)
Fair value of plan assets at end of period	134,262
Funded status	(27,783)
Accumulated benefit obligation	$ 162,045
Discount rate (as a percent)	3.00%			3.50%
Adjusted funding target attainment percentage			92.30%
Supplemental Benefit Plan
Components of net periodic benefit cost
Interest cost	$ 32	31
Amortization of net actuarial loss	38	40
Net periodic benefit cost	70	71
Change in projected benefit obligation
Interest cost	32	31
Postretirement Health Benefit Plan
Components of net periodic benefit cost
Service cost	107	101
Interest cost	254	228
Amortization of prior service credit	(47)	(47)
Amortization of net actuarial loss	176	213
Net periodic benefit cost	490	495
Change in projected benefit obligation
Interest cost	$ 254	$ 228