STOCK-BASED COMPENSATION - Other (Details) - Stock options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Stock based awards
Weighted-average remaining life of exercisable stock options	4 years 4 months 10 days
Exercisable at the end of the period (in dollars)	$ 30.9
Exercisable Stock Options, Weighted-Average Exercise Price (in dollars per share)	$ 56.31
Options vested and expected to vest at the end of the period (in shares)	1,306,087
Options vested or expected to vest, aggregate intrinsic value (in dollars)	$ 10.6
Options vested or expected to vest, weighted-average exercise price (in dollars per share)	$ 62.49
Unrecognized compensation cost (in dollars)	$ 7.3
Period over which unrecognized compensation cost is expected to be recognized	2 years 3 months 18 days
Total intrinsic value of options exercised (in dollars)	$ 9.9	$ 13.1	$ 6.3
Grant date fair value of shares vested (in dollars)	$ 8.8	$ 6.7	$ 9.6