STOCKHOLDERS' EQUITY (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2018 USD ($) Vote shares	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($) shares	Jan. 07, 2016 USD ($)
Capital Stock Activity [Rollforward]
Beginning Balance (in shares)	35,230,742	34,261,304	33,489,181
Exercise of stock options (in shares)	487,915	818,640	606,562
Restricted stock under EIP and OIP, net of forfeitures (in shares)	93,817	81,047	86,277
Restricted stock under Deposit Share Plan, net of forfeitures (in shares)			1,847
Common stock under ESPP (in shares)	49,991	69,751	77,437
Ending Balance (in shares)	35,862,465	35,230,742	34,261,304
Treasury Stock [Abstract]
Beginning Balance (in shares)	9,948,190	9,744,642	9,041,678
Repurchases of common stock under share repurchase plans (in shares)	369,791	167,809	636,839
Repurchases of common stock - other (in shares)	38,166	35,739	66,125
Ending Balance (in shares)	10,356,147	9,948,190	9,744,642
Number of votes each common stockholder is entitled to on matter submitted to a vote of stockholders | Vote	1
Number of authorized shares of common stock (in shares)	200,000,000	200,000,000
Share repurchase program, value of shares remaining to be repurchased | $	$ 81,271
Cost of shares repurchased | $	$ 40,726	$ 12,035	$ 25,980
Share Repurchase Program [Member]
Treasury Stock [Abstract]
Share repurchase program, value of shares authorized to be repurchased | $				$ 150,000
Prior Repurchase Program [Member]
Treasury Stock [Abstract]
Share repurchase program, value of shares authorized to be repurchased | $				$ 75,000