Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Net Income	$ 87,898	$ 105,196	$ 90,258
Net losses on derivative instruments (net of tax of $4,783 and $7,712, respectively)	(6,744)	(10,874)	0
Reclassifications of net losses on derivative instruments (net of tax of $(766), $(483), and $(483), respectively)	1,111	681	681
Benefit plans (net of tax of $1,948, $479 and $11,134, respectively)	(2,745)	(674)	(15,699)
Reclassification of benefit plans actuarial losses and prior service costs to net income (net of tax of $(333), $(304) and $(2,414), respectively)	394	430	3,406
Reclassification of pension plans actuarial losses and prior service costs to regulatory assets (net of tax of $(59,078))	0	0	83,302
Comprehensive income	$ 79,914	$ 94,759	$ 161,948