INCOME TAXES - Reconciliation of income tax and unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Reconciliation of income tax computed at the U.S. federal statutory tax rate to income tax expense
Tax expense at U.S. statutory rate	$ (2,616)	$ 25,169	$ 31,294
State income taxes, net of federal tax effect	(1,199)	(34)	111
Nondeductible expenses	7,828	1,555	1,319
Change in reserve for tax contingencies	1,320	(1,192)	(601)
Change in deferred tax asset valuation allowance	(9,228)	37,589	921
Foreign income taxed at less than statutory rate	(2,999)	(11,924)	(12,783)
Research and development credits	(2,542)	(2,248)	(584)
Other	224	82	154
Provision for income taxes	(9,212)	48,997	$ 19,831
Compensation expense not expected to be deductible for tax purposes	6,300
Change in valuation allowance	6,900	35,800
Research tax credit	$ 1,000	$ 1,200