COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Letter of credit
Operating Leased Assets [Line Items]
Outstanding letters of credit	$ 11.1		$ 11.1
Tractor, trailer and other revenue equipment
Operating Leased Assets [Line Items]
Rent expense	4.7	$ 3.5	12.7	$ 9.2
Office and Terminals
Operating Leased Assets [Line Items]
Rent expense	$ 2.1	$ 0.7	$ 4.5	$ 2.0