SHARE-BASED COMPENSATION PLANS, Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Stock Options Activity [Roll Forward]
Exercised (in shares)	(487,915)	(818,640)	(606,562)
Stock Options [Member]
Stock Options Activity [Roll Forward]
Outstanding, beginning of period (in shares)	1,517,061
Granted (in shares)	152,282
Exercised (in shares)	(488,029)
Forfeited or canceled (in shares)	(49,833)
Outstanding, end of period (in shares)	1,131,481	1,517,061
Exercisable, end of period ( in shares)	552,969
Expected to vest, end of period (in shares)	575,758
Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of period (in dollars per share)	$ 44.17
Granted (in dollars per share)	95.19
Exercised (in dollars per share)	39.45
Forfeited or canceled (in dollars per share)	53.09
Outstanding, end of period (in dollars per share)	52.68	$ 44.17
Exercisable, end of period (in dollars per share)	41.57
Expected to vest, end of period (in dollars per share)	$ 63.16
Additional Disclosures [Abstract]
Weighted average remaining contractual term, outstanding, end of period	6 years 9 months 18 days
Weighted average remaining contractual term, exercisable, end of period	5 years 6 months
Weighted average remaining contractual term, expected to vest, end of period	8 years
Aggregate intrinsic value, outstanding, end of period	$ 57,212
Aggregate intrinsic value, exercisable, end of period	34,063
Aggregate intrinsic value, expected to vest, end of period	23,120
Total intrinsic value of options exercised	30,345	$ 25,213	$ 12,317
Cash received from options exercised	19,247	27,666	16,623
Actual tax benefit realized for the tax deductions from options exercised	7,503	8,743	4,076
Total fair value of stock options vested	5,008	$ 5,300	$ 7,880
Total unrecognized share-based compensation expense	$ 6,723
Compensation cost, weighted-average period for recognition	2 years 3 months 18 days