Commitments And Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2019 USD ($)
Site Contingency [Line Items]
Estimate minimum liability for environmental remediation	$ 7.0
Future purchase obligation first year	256.4
Future purchase obligation second year	78.5
Future purchase obligation third year	111.2
Future purchase obligation fourth year	110.8
Future purchase obligation fifth year	115.6
Future purchase obligation thereafter	1,098.8
Operating lease commitment first year	12.4
Operating lease commitment second year	2.8
Operating lease commitment third year	2.3
Operating lease commitment fourth year	2.3
Operating lease commitment fifth year	2.2
Operating lease commitment thereafter	9.7
Former Manufactured Gas Plant Site New York [Member]
Site Contingency [Line Items]
Estimate minimum liability for environmental remediation	$ 3.8
Environmental Site Remediation Costs [Member]
Site Contingency [Line Items]
Rate recovery period	3 years
Pipeline And Storage, Gathering And Utility Segments [Member]
Site Contingency [Line Items]
Contract commitments first year	$ 97.5
Contract commitments second year	34.9
Contract commitments third year	6.0
Contract commitments fourth year	3.3
Contract commitments fifth year	3.3
Contract commitments thereafter	11.6
Exploration And Production [Member]
Site Contingency [Line Items]
Contract commitments first year	104.3
Contract commitments second year	22.2
Contract commitments third year	$ 1.7