Commitments And Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2017 USD ($)
Site Contingency [Line Items]
Estimate minimum liability for environmental remediation	$ 3.1
Project Costs	75.8
Future purchase obligation first year	262.4
Future purchase obligation second year	84.6
Future purchase obligation third year	77.9
Future purchase obligation fourth year	70.9
Future purchase obligation fifth year	61.7
Future purchase obligation thereafter	504.9
Operating lease commitment first year	10.8
Operating lease commitment second year	4.6
Operating lease commitment third year	3.7
Operating lease commitment fourth year	2.2
Operating lease commitment fifth year	1.5
Operating lease commitment thereafter	$ 1.9
Environmental Site Remediation Costs [Member]
Site Contingency [Line Items]
Rate recovery period	4 years
Pipeline And Storage, Gathering And Utility Segments [Member]
Site Contingency [Line Items]
Contract commitments first year	$ 61.7
Contract commitments second year	0.7
Contract commitments third year	0.2
Contractual commitments fourth year	0.3
Contractual commitments fifth year	0.3
Contractual commitments thereafter	1.1
Exploration And Production [Member]
Site Contingency [Line Items]
Contract commitments first year	79.5
Contract commitments second year	98.0
Contract commitments third year	$ 17.1