SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		9 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2013	Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance as of January 1, 2013			$ (10,688)
Other comprehensive income, excluding reclassifications, net of tax of $(611), $(4), $-, $(615)			891
Amounts reclassified from accumulated other comprehensive income, net of tax of $155, $21 $(405), $(229)			327
Other comprehensive income	287	320	1,218		1,306	724
Ending balance as of March 31, 2013	(9,470)		(9,470)		(9,470)
Other comprehensive income, excluding reclassifications, tax			(615)
Amounts reclassified from accumulated other comprehensive income, tax			(229)
Net current-period other comprehensive income, tax			(844)
Unrealized Gain on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance as of January 1, 2013			4,601
Other comprehensive income, excluding reclassifications, net of tax of $(611), $(4), $-, $(615)			885
Amounts reclassified from accumulated other comprehensive income, net of tax of $155, $21 $(405), $(229)			(225)	[1]
Other comprehensive income			660
Ending balance as of March 31, 2013	5,261		5,261		5,261
Other comprehensive income, excluding reclassifications, tax			(611)
Amounts reclassified from accumulated other comprehensive income, tax			155
Net current-period other comprehensive income, tax			(456)
Net Unrealized Gain on Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance as of January 1, 2013			41
Other comprehensive income, excluding reclassifications, net of tax of $(611), $(4), $-, $(615)			6
Amounts reclassified from accumulated other comprehensive income, net of tax of $155, $21 $(405), $(229)			(40)	[2]
Other comprehensive income			(34)
Ending balance as of March 31, 2013	7		7		7
Other comprehensive income, excluding reclassifications, tax			(4)
Amounts reclassified from accumulated other comprehensive income, tax			21
Net current-period other comprehensive income, tax			17
Adjustment to Postemployment Benefit Obligation [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance as of January 1, 2013			(15,330)
Other comprehensive income, excluding reclassifications, net of tax of $(611), $(4), $-, $(615)			0
Amounts reclassified from accumulated other comprehensive income, net of tax of $155, $21 $(405), $(229)			592	[3]
Other comprehensive income			592
Ending balance as of March 31, 2013	(14,738)		(14,738)		(14,738)
Other comprehensive income, excluding reclassifications, tax			0
Amounts reclassified from accumulated other comprehensive income, tax			(405)
Net current-period other comprehensive income, tax			$ (405)

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

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

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