INCOME TAXES (Tax Reform Act) (Details) - USD ($) $ in Millions	2 Months Ended	3 Months Ended		4 Months Ended	6 Months Ended		12 Months Ended
	Feb. 28, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Impact of Tax Reform Act
Statutory federal rate (as a percent)	32.74%				21.00%		35.00%
Provisional reduction of deferred tax liabilities due to Tax Reform Act					$ 2.6		$ 24.5
State tax, low end of range of rate (as a percent)					6.00%
State tax, high end of range of rate (as a percent)					6.50%
Effective tax (benefit) expense rate (as a percent)		(68.00%)	34.60%		(15.00%)	27.10%
Provisional reduction in current income tax expense due Tax Reform Act reflecting use of fiscal year rather than calendar year federal income tax filing							1.3
Projected combined tax rate based on federal statutory rate and applicable state tax rates (as a percent)				26.50%
Alternative fuel tax credit							$ 1.2
Maximum
Impact of Tax Reform Act
Provisional reduction of deferred tax liabilities due to Tax Reform Act		$ 0.1