ACCRUED EXPENSES (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
ACCRUED EXPENSES
Accrued compensation	$ 15,841	$ 20,128
Accrued vacation pay	40,473	39,507
Taxes other than income	7,366	6,920
Loss, injury, damage, and workers' compensation claims reserves	86,969	75,801
Current portion of supplemental pension benefits		1,126
Other	8,019	8,405
Total accrued expenses	$ 158,668	$ 151,887