Other Income, Net - Schedule of Other Income, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Component of Operating Income [Abstract]
Non-tariff service income	$ 4,760	$ 2,670	$ 2,706
Construction service income	2,175	0	0
Sale of HVAC Business	1,065	0	0
Interest income	0	1,388	500
Other, net	869	301	1,622
Total other income, net	$ 8,869	$ 4,359	$ 4,828