SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (10,771)
Other comprehensive income, excluding reclassifications, net of tax of $(485), $16, $(5,124), $(5,593)	8,201
Amounts reclassified from accumulated other comprehensive income, net of tax of $155, $7, $(810), $(648)	949
Other comprehensive income (loss)	9,150		(167)	1,403
Balance at end of period	(1,621)		(10,771)
Tax on other comprehensive income before reclassifications	(5,593)
Tax on amounts reclassified from accumulated other comprehensive income	(648)
Tax on net current-period other comprehensive income	(6,241)
Unrealized Gain on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	4,921
Other comprehensive income, excluding reclassifications, net of tax of $(485), $16, $(5,124), $(5,593)	703
Amounts reclassified from accumulated other comprehensive income, net of tax of $155, $7, $(810), $(648)	(224)	[1]
Other comprehensive income (loss)	479
Balance at end of period	5,400
Tax on other comprehensive income before reclassifications	(485)
Tax on amounts reclassified from accumulated other comprehensive income	155
Tax on net current-period other comprehensive income	(330)
Net Unrealized Gain on Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	51
Other comprehensive income, excluding reclassifications, net of tax of $(485), $16, $(5,124), $(5,593)	(28)
Amounts reclassified from accumulated other comprehensive income, net of tax of $155, $7, $(810), $(648)	(11)	[2]
Other comprehensive income (loss)	(39)
Balance at end of period	12
Tax on other comprehensive income before reclassifications	16
Tax on amounts reclassified from accumulated other comprehensive income	7
Tax on net current-period other comprehensive income	23
Adjustment to Postemployment Benefit Obligation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(15,743)
Other comprehensive income, excluding reclassifications, net of tax of $(485), $16, $(5,124), $(5,593)	7,526
Amounts reclassified from accumulated other comprehensive income, net of tax of $155, $7, $(810), $(648)	1,184	[3]
Other comprehensive income (loss)	8,710
Balance at end of period	(7,033)
Tax on other comprehensive income before reclassifications	(5,124)
Tax on amounts reclassified from accumulated other comprehensive income	(810)
Tax on net current-period other comprehensive income	$ (5,934)

[1] Reclassified to other income in the Consolidated Statements of Operations.

[2] Reclassified to gas purchases in the Consolidated Statements of Operations.

[3] Included in the computation of net periodic pension cost, a component of O&M expense in the Consolidated Statements of Operations.