Other Income, Net - Schedule of Other Income, Net (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Component of Operating Income [Abstract]
Non-tariff service income	$ 2,670	$ 2,706	$ 2,653
Interest income	1,388	500	572
Other, net	301	1,622	1,764
Total other income, net	$ 4,359	$ 4,828	$ 4,989

The amount of interest income and other income recognized during the period. Included in this element is interest derived from investments in debt securities, cash and cash equivalents, and other investments which reflect the time value of money or transactions in which the payments are for the use or forbearance of money and other income from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business).

No definition available.

Name:	us-gaap_InterestAndOtherIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration