STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Statement of Other Comprehensive Income [Abstract]
Net Income	$ 25,743	$ 21,697
Net gains (losses) on cash flow hedging derivative instruments:
Net hedging gain arising during the period	57	50
Reclassification adjustment for gains included in net income	(47)	(14)
Net unrealized gains on cash flow hedging derivative instruments	10	36
Defined benefit pension and other postretirement benefit plans:
Amortization of actuarial loss included in net periodic pension and postretirement benefit cost	90	91
Other Comprehensive Income, Before Tax	100	127
Income Tax Expense Related to Items of Other Comprehensive Income	48	49
Other Comprehensive Income, Net of Tax	52	78
Comprehensive Income	$ 25,795	$ 21,775