Inventories (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Inventory, Net [Abstract]
Total inventories	$ 89,661	$ 67,334
Gas Utility natural gas [Member]
Inventory, Net [Abstract]
Total inventories	78,950	57,663
Materials, supplies and other [Member]
Inventory, Net [Abstract]
Total inventories	$ 10,711	$ 9,671