OPERATING SEGMENT DATA - Capital expenditures, depreciation and amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	$ 252,411	$ 229,209	$ 116,938
DEPRECIATION AND AMORTIZATION EXPENSE	145,349	138,159	122,560
Amortization of intangibles	12,829	12,920	5,357
Research and development costs	52,400	40,800
Other and eliminations
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	37,752	77,720	11,193
DEPRECIATION AND AMORTIZATION EXPENSE	20,814	20,107	17,374
Assets acquired through notes payable		3,400
Other and eliminations | Service center
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS		37,500
Asset Based | Operating Segments
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	207,072	137,117	96,180
DEPRECIATION AND AMORTIZATION EXPENSE	104,165	97,322	93,799
Assets acquired through notes payable	33,500	79,000	59,700
Asset-Light | Operating Segments
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	7,587	14,372	9,565
DEPRECIATION AND AMORTIZATION EXPENSE	20,370	20,730	11,387
Amortization of intangibles	$ 12,800	$ 12,900	$ 5,300