Commitments And Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2012
Site Contingency [Line Items]
Estimated minimum liability for environmental remediation	$ 15.4
Estimated maximum liability for environmental remediation	19.6
Rate recovery period	10 years
Future purchase obligation first year	278.1
Future purchase obligation second year	68.1
Future purchase obligation third year	64.1
Future purchase obligation fourth year	60.2
Future purchase obligation fifth year	32.3
Future purchase obligation thereafter year	66.6
Operating lease commitment first year	38.7
Operating lease commitment second year	37.0
Operating lease commitment third year	13.2
Operating lease commitment fourth year	5.8
Operating lease commitment fifth year	5.7
Operating lease commitment thereafter year	8.5
Former Manufactured Gas Plant Site [Member]
Site Contingency [Line Items]
Estimated minimum liability for environmental remediation	14.0
Exploration And Production [Member]
Site Contingency [Line Items]
Contract commitments first year	60.7
Contract commitments second year	11.4
Pipeline And Storage And All Other [Member]
Site Contingency [Line Items]
Contract commitments first year	$ 40.7