EMPLOYEE BENEFIT PLANS, COMPONENTS OF NET PERIODIC COST (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Special termination benefit	$ 5,000
Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		$ 7,485	[1]	$ 6,143	[1]	$ 6,871
Interest cost		10,199	[1]	10,066	[1]	8,942
Expected return on plan assets		(17,090)		(15,475)		(14,825)
Recognized actuarial loss		6,985		5,596		7,646
Prior service cost (credit) amortization		111		111		108
Recognized net initial obligation		0		0		0
Net periodic benefit cost		7,690		6,441		8,742
Special termination benefit		0	[1]	2,814	[1]	0
Net periodic benefit cost recognized as expense		7,690		9,255		8,742
OPEB [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		4,253		3,923		4,686
Interest cost		5,739		5,734		5,148
Expected return on plan assets		(4,977)		(4,174)		(3,653)
Recognized actuarial loss		2,943		2,500		3,857
Prior service cost (credit) amortization		(364)		(357)		(355)
Recognized net initial obligation		0		11		26
Net periodic benefit cost		7,594		7,637		9,709
Special termination benefit		0		648		0
Net periodic benefit cost recognized as expense		$ 7,594		$ 8,285		$ 9,709

[1] Includes the Company's PEP.