STOCK-BASED COMPENSATION - Restricted Stock and Restricted Stock Unit Activity (Details) - Restricted Stock Awards	12 Months Ended
	Sep. 30, 2017 $ / shares shares
Performance Vesting
Shares/ Units
Nonvested at beginning of period (in shares) | shares	510,583
Vested (in shares) | shares	(78,825)
Forfeited (in shares) | shares	(64,128)
Nonvested at end of period (in shares) | shares	282,015
Weighted Average Grant Date Fair Value Per Share
Nonvested at beginning of period (in dollars per share) | $ / shares	$ 40.37
Vested (in dollars per share) | $ / shares	42.37
Forfeited (in dollars per share) | $ / shares	33.03
Nonvested at end of period (in dollars per share) | $ / shares	$ 56.32
Time Vesting
Shares/ Units
Nonvested at beginning of period (in shares) | shares	132,779
Granted (in shares) | shares	44,090
Vested (in shares) | shares	(58,200)
Forfeited (in shares) | shares	(7,729)
Nonvested at end of period (in shares) | shares	110,940
Weighted Average Grant Date Fair Value Per Share
Nonvested at beginning of period (in dollars per share) | $ / shares	$ 49.83
Granted (in dollars per share) | $ / shares	63.15
Vested (in dollars per share) | $ / shares	47.67
Forfeited (in dollars per share) | $ / shares	55.58
Nonvested at end of period (in dollars per share) | $ / shares	$ 55.85
Maximum | Performance Vesting
Shares/ Units
Granted (in shares) | shares	196,400
Nonvested at end of period (in shares) | shares	564,030
Weighted Average Grant Date Fair Value Per Share
Granted (in dollars per share) | $ / shares	$ 45.01
Nonvested at end of period (in dollars per share) | $ / shares	$ 42.51