LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Notes Payable (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Notes payable \| Revenue equipment and software
Financing Arrangements
Assets financed during the period under promissory note arrangements	$ 61.8	$ 90.8

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585

Name:	us-gaap_ProceedsFromIssuanceOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration