INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current provision:
Federal									$ 9,156	$ 18,063	$ 12,739
State									165	23	865
Foreign									2,124	1,657	413
Current tax provision									11,445	19,743	14,017
Deferred provision (benefit):
Federal									12,914	1,575	(10,335)
State									3,589	3,366	160
Foreign									(68)	(249)	(192)
Deferred tax provision (benefit)									16,435	4,692	(10,367)
Total provision (benefit) for income taxes	$ 1,878	$ 12,892	$ 12,942	$ 167	$ 5,097	$ 12,938	$ 10,163	$ (3,762)	27,880	24,435	3,650
Significant components of the deferred tax provision or benefit
Amortization, depreciation, and basis differences for property, plant and equipment and other long-lived assets									21,098	3,579	(13,137)
Amortization of intangibles									(3,184)	(2,934)	(3,048)
Changes in reserves for workers' compensation and cargo claims									(674)	(1,970)	(1,751)
Revenue recognition									7	361	(1,704)
Allowance for doubtful accounts									307	(501)	516
Foreign tax credit carryforward utilized									434	665	71
Nonunion pension and other retirement plans									(234)	(1,595)	3,493
Deferred compensation plans									541	350	530
Federal net operating loss carryforwards utilized									70	4,472	4,207
State net operating loss carryforwards utilized									623	2,812	254
State depreciation adjustments									(657)	(539)	569
Share-based compensation									(621)	959	(1,437)
Valuation allowance increase (decrease)									22	(696)	(1,436)
Leases									(969)	237	612
Other accrued expenses									1,256	(362)	3,284
Other									(1,584)	(146)	(1,390)
Deferred tax provision (benefit)									$ 16,435	$ 4,692	$ (10,367)