STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Statement of Income and Comprehensive Income [Abstract]
Net Income	$ 21,697	$ 21,455
Net gains (losses) on cash flow hedging derivative instruments:
Net hedging gain arising during the period	50	173
Reclassification adjustment for gains included in net income	(14)	(49)
Net unrealized gains on cash flow hedging derivative instruments	36	124
Defined benefit pension and other postretirement benefit plans:
Amortization of actuarial loss included in net periodic pension and postretirement benefit cost	91	107
Other Comprehensive Income, Before Tax	127	231
Income Tax Expense Related to Items of Other Comprehensive Income	49	89
Other Comprehensive Income, Net of Tax	78	142
Comprehensive Income	$ 21,775	$ 21,597