Derivative Commodities and Disclosures (Details) MWh in Thousands, MMBTU in Thousands, Gallon in Thousands, $ in Thousands		Sep. 30, 2016 USD ($) MMBTU Gallon MWh	Sep. 30, 2015 MMBTU Gallon MWh
Derivative
Derivative Asset, Collateral, Obligation to Return Cash, Offset	[1]	$ 24
Derivatives in a net liability position		200
Collateral Already Posted, Aggregate Fair Value		0
Additional Collateral, Aggregate Fair Value		$ 3,800
Electricity (MWh) | Long [Member]
Derivative
Derivative, Nonmonetary Notional Amount | MWh		130	350
Electricity (MWh) | Short [Member]
Derivative
Derivative, Nonmonetary Notional Amount | MWh		143	160
Natural Gas (MMBTU) | Long [Member]
Derivative
Derivative, Nonmonetary Notional Amount | MMBTU		7,977	14,570
Natural Gas (MMBTU) | Short [Member]
Derivative
Derivative, Nonmonetary Notional Amount | MMBTU		70	944
Diesel Fuel (Gallons) | Long [Member]
Derivative
Derivative, Nonmonetary Notional Amount | Gallon		267	61

[1] Excludes unrealized gains or losses on derivatives, which are recorded on the balance sheet as regulatory assets or regulatory liabilities.