PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Details) (USD $)	3 Months Ended		3 Months Ended		12 Months Ended	3 Months Ended
	Mar. 31, 2012 ABF plan Y	Jan. 02, 2012 ABF	Mar. 31, 2012 Nonunion Defined Benefit Pension Plan	Mar. 31, 2011 Nonunion Defined Benefit Pension Plan	Dec. 31, 2011 Nonunion Defined Benefit Pension Plan	Mar. 31, 2012 Supplemental Benefit Pension Plan	Mar. 31, 2011 Supplemental Benefit Pension Plan	Mar. 31, 2012 Postretirement Health Benefit Plan	Mar. 31, 2011 Postretirement Health Benefit Plan
Components of net periodic benefit cost
Service cost			$ 2,297,000	$ 2,164,000				$ 79,000	$ 56,000
Interest cost			2,173,000	2,489,000		52,000	97,000	187,000	195,000
Expected return on plan assets			(3,016,000)	(3,146,000)
Amortization of prior service credit								(48,000)	(48,000)
Amortization of net actuarial loss and other			2,692,000	1,730,000		51,000	82,000	104,000	28,000
Net periodic benefit cost			4,146,000	3,237,000	12,900,000	103,000	179,000	322,000	231,000
Voluntary contribution for prior plan year			3,000,000
Funding target attainment percentage (as a percent)			80.00%
Contribution made for current plan year			15,000,000
Estimated nonunion defined benefit pension plan expense for the current fiscal year			$ 16,600,000
Multiemployer Plans
Period of collective bargaining agreement (in years)	5
Number of multiemployer pension plans to which ABF currently contributes	25
Maximum required increase in employer's contribution to multiemployer plans that enter reorganization status (as a percent)	7.00%
Proportion of multiemployer pension plan contributions made to Central States Pension Fund (as a percent)	50.00%
Central States Pension Fund actuarially certified funded percentage (as a percent)		58.90%