STOCK-BASED COMPENSATION - Other (Details) - Stock options - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019
Stock based awards
Weighted average fair value of options granted (in dollars per share)		$ 17.78
Total intrinsic value of options exercised (in dollars)	$ 0.1		$ 7.7
Unrecognized compensation cost (in dollars)	$ 4.8		$ 4.8
Period over which unrecognized compensation cost is expected to be recognized			2 years 2 months 12 days

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

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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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- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

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-Publisher FASB
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