STOCK-BASED COMPENSATION - Compensation cost (Details) - USD ($) $ in Thousands	3 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Stock based awards
Compensation expense (in dollars)	$ 7,158	$ 7,087
Stock options
Stock based awards
The period from the grant date after which options expire	10 years
Compensation expense (in dollars)	$ 1,416	1,963
Restricted stock
Stock based awards
Number of shares granted	473,000
Compensation expense (in dollars)	$ 5,742	$ 5,124
2016 Plan \| Stock options
Stock based awards
Number of shares granted	0
2016 Plan \| Restricted stock
Stock based awards
Number of shares granted	472,987
2010 Plan \| Restricted stock
Stock based awards
Number of shares granted	142,603

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Gross number of share options (or share units) granted during the period.

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- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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