INCOME TAXES (Tax Reform Act) (Details) - USD ($)	1 Months Ended	2 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Feb. 28, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Impact of Tax Reform Act
Statutory federal rate (as a percent)		32.74%	21.00%		35.00%
Projected combined tax rate based on federal statutory rate and applicable state tax rates (as a percent)	$ 25.80
Provisional reduction of deferred tax liabilities due to Tax Reform Act			$ 2,600,000		$ 24,500,000
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 rate (as a percent)			10.70%	41.40%
Provisional reduction in current income tax expense due Tax Reform Act reflecting use of fiscal year rather than calendar year federal income tax filing					$ 1,300,000
Alternative fuel tax credit			$ 1,200,000