Other Income, Net (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Component of Other Income, Nonoperating [Line Items]
Other Operating Income	$ 4,828	$ 4,989	$ 10,764
Non-tariff service income [Member]
Component of Other Income, Nonoperating [Line Items]
Total other income, net	2,706	2,653	6,422
Interest income [Member]
Component of Other Income, Nonoperating [Line Items]
Total other income, net	500	572	467
Postretirement benefit plan curtailment gain [Member]
Component of Other Income, Nonoperating [Line Items]
Total other income, net	0	0	3,245
Other [Member]
Component of Other Income, Nonoperating [Line Items]
Total other income, net	$ 1,622	$ 1,764	$ 630