COMMON STOCK EQUITY - ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance as of beginning of period	$ (1,621)		$ (10,771)
Other comprehensive (loss), before reclassifications, net of tax	(406)		(380)
Losses reclassified from accumulated other comprehensive income, net of tax	223		463
Other comprehensive (loss) income	(183)		83
Balance as of end of period	(1,804)		(10,688)
Tax on other comprehensive income before reclassifications	270		256
Tax on amounts reclassified from accumulated other comprehensive income	(147)		(232)
Tax on net current-period other comprehensive income	123		24
Available for Sale Securities [Member]
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance as of beginning of period	5,400		4,921
Other comprehensive (loss), before reclassifications, net of tax	(310)		(320)
Losses reclassified from accumulated other comprehensive income, net of tax	0	[1]	0	[1]
Other comprehensive (loss) income	(310)		(320)
Balance as of end of period	5,090		4,601
Tax on other comprehensive income before reclassifications	214		221
Tax on amounts reclassified from accumulated other comprehensive income	0		0
Tax on net current-period other comprehensive income	214		221
Cash Flow Hedges [Member]
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance as of beginning of period	12		51
Other comprehensive (loss), before reclassifications, net of tax	(96)		(60)
Losses reclassified from accumulated other comprehensive income, net of tax	62	[2]	50	[2]
Other comprehensive (loss) income	(34)		(10)
Balance as of end of period	(22)		41
Tax on other comprehensive income before reclassifications	56		35
Tax on amounts reclassified from accumulated other comprehensive income	(36)		(29)
Tax on net current-period other comprehensive income	20		6
Postemployment Benefit Obligation [Member]
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance as of beginning of period	(7,033)		(15,743)
Other comprehensive (loss), before reclassifications, net of tax	0		0
Losses reclassified from accumulated other comprehensive income, net of tax	161	[3]	413	[3]
Other comprehensive (loss) income	161		413
Balance as of end of period	(6,872)		(15,330)
Tax on other comprehensive income before reclassifications	0		0
Tax on amounts reclassified from accumulated other comprehensive income	(111)		(203)
Tax on net current-period other comprehensive income	$ (111)		$ (203)

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

[2] Consists of realized losses related to foreign currency derivatives, which are reclassified to gas purchases in the Unaudited Condensed Consolidated Statements of Operations.

[3] Included in the computation of net periodic pension cost, a component of operations and maintenance expense in the Unaudited Condensed Consolidated Statements of Operations.