INCOME TAXES (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015
Deferred tax assets:
Net operating loss carryforwards	$ 0	$ 22,930
Tax credit carryforwards	2,831	2,464
Stock option compensation expense	11,801	10,924
Debt issuance costs	251	221
Basis difference in fleet spares	4,310	0
Book accruals	3,189	3,064
Deferred tax assets	22,382	39,603
Deferred tax liabilities:
Difference in book and tax basis of equipment	(209)	(209)
Deferred dividend withholding tax	(1,202)	(907)
Other timing differences	(199)	(1,422)
Deferred tax liabilities	(1,610)	(2,538)
Net deferred tax assets (liabilities) before valuation allowance	20,772	37,065
Valuation allowance	(21,808)	(38,573)
Net deferred tax liabilities	$ (1,036)	$ (1,508)