EMPLOYEE BENEFIT PLANS, COMPONENTS OF NET PERIODIC COST (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2014
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 7,591	[1]	$ 7,485	[1]	$ 6,143
Interest cost	11,342	[1]	10,199	[1]	10,066
Expected return on plan assets	(20,118)		(17,090)		(15,475)
Recognized actuarial loss	7,281		6,985		5,596
Prior service cost (credit) amortization	111		111		111
Recognized net initial obligation	0		0		0
Net periodic benefit cost	6,207		7,690		6,441
Special termination benefit	0		0		2,814
Net periodic benefit cost recognized as expense	6,207		7,690		9,255
OPEB
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	4,521		4,253		3,923
Interest cost	6,256		5,739		5,734
Expected return on plan assets	(4,845)		(4,977)		(4,174)
Recognized actuarial loss	3,274		2,943		2,500
Prior service cost (credit) amortization	(365)		(364)		(357)
Recognized net initial obligation	0		0		11
Net periodic benefit cost	8,841		7,594		7,637
Special termination benefit	0		0		648
Net periodic benefit cost recognized as expense	$ 8,841		$ 7,594		$ 8,285

[1] Includes the Company’s PEP.