INCOME TAXES Deferred Tax Assets Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Components of Deferred Tax Assets and Liabilities [Abstract]
Investment tax credits	$ 32,002	$ 3,353
Deferred service contract revenue	3,185	3,191
Incentive compensation	7,666	3,775
Over-recovered gas costs	0	1,866
Other	8,893	5,451
Total deferred tax assets	51,746	17,636
Property related items	(284,871)	(258,501)
Remediation costs	(24,018)	(30,459)
Equity investments	(31,610)	(28,255)
Post employment benefits	(8,520)	(4,914)
Fair value of derivatives	(5,461)	(16,602)
Conservation incentive plan	(11,200)	(3,697)
Under-recoverd gas costs	(2,835)	0
Other	(4,514)	(1,492)
Total deferred tax (liabilities)	(373,029)	(343,920)
Total net deferred tax (liabilities)	$ (321,283)	$ (326,284)