INCOME TAXES, Reconciliation of Income taxes Computed at the Statutory Federal Income Tax Rate to Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
INCOME TAXES [Abstract]
Additions or reductions to gross unrecognized tax benefits									$ 0
Reconciliation of income taxes to the statutory rate [Abstract]
Statutory federal income tax rate									21.00%	31.50%	35.00%
Income tax expense computed at the U.S. statutory federal rate									$ 18,139	$ 26,505	$ 30,134
Effect of federal reduction of statutory rate									0	(1,654)	0
State income tax expense - net of federal benefit									4,795	3,842	4,193
Non-deductible executive compensation									630	658	512
Other									(526)	(582)	717
Provision for income taxes	$ 4,974	$ 5,880	$ 6,889	$ 5,295	$ 9,270	$ 678	$ 11,466	$ 7,355	$ 23,038	$ 28,769	$ 35,556
Effective income tax rate									26.70%	34.30%	41.30%