PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Details) (USD $)	3 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Jan. 31, 2014 person	Jan. 01, 2014	Jan. 01, 2015	Dec. 31, 2014
Components of net periodic benefit cost
Pension settlement expense	$ 1,119,000	$ 3,691,000
Pension settlement expense, net of tax	684,000	2,255,000
Multiemployer pension plans | Freight Transportation (ABF Freight)
Multiemployer Plans
Number of multiemployer plans to which ABF Freight currently contributes	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 made to Central States Pension Fund (as a percent)	50.00%
Actuarially certified funded percentage of multiemployer pension plan				48.40%
Nonunion Defined Benefit Pension Plan
Components of net periodic benefit cost
Interest cost	1,320,000	1,720,000
Expected return on plan assets	(2,402,000)	(2,831,000)
Pension settlement expense	1,119,000	3,691,000
Amortization of net actuarial loss	821,000	498,000
Net periodic benefit cost	858,000	3,078,000
Number of plan participants for which vested pension benefits were settled			375
Premium paid to purchase nonparticipating annuity contract			25,400,000
Lump-sum distributions	7,600,000	14,100,000
Pension settlement expense, net of tax	700,000	2,300,000
Amortization period for unrecognized net actuarial loss	8 years
Change in projected benefit obligation
Projected benefit obligation at the beginning of the period	174,410,000
Interest cost	1,320,000	1,720,000
Actuarial loss	4,171,000
Benefits paid	(7,665,000)
Projected benefit obligation at the end of the period	172,236,000
Change in plan assets
Fair value of plan assets at beginning of period	158,265,000
Actual return on plan assets	3,577,000
Employer contributions	50,000
Benefits paid	(7,665,000)
Fair value of plan assets at end of period	154,227,000
Funded status	(18,009,000)
Accumulated benefit obligation	172,236,000
Discount rate (as a percent)	3.00%					3.20%
Adjusted funding target attainment percentage					108.10%
Supplemental Benefit Plan
Components of net periodic benefit cost
Interest cost	31,000	49,000
Amortization of net actuarial loss	40,000	56,000
Net periodic benefit cost	71,000	105,000
Change in projected benefit obligation
Interest cost	31,000	49,000
Postretirement Health Benefit Plan
Components of net periodic benefit cost
Service cost	101,000	70,000
Interest cost	228,000	197,000
Amortization of prior service credit	(47,000)	(47,000)
Amortization of net actuarial loss	213,000	23,000
Net periodic benefit cost	495,000	243,000
Change in projected benefit obligation
Interest cost	$ 228,000	$ 197,000