Commitments and Contingencies (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Recorded Unconditional Purchase Obligation [Line Items]
Estimate minimum liability for environmental remediation	$ 2,400
Other regulatory liabilities	749,574	$ 711,697
Future purchase obligation first year	215,600
Future purchase obligation second year	88,400
Future purchase obligation third year	93,200
Future purchase obligation fourth year	113,100
Future purchase obligation fifth year	116,400
Future purchase obligation thereafter	663,200
Environmental Site Remediation Costs
Recorded Unconditional Purchase Obligation [Line Items]
Other regulatory liabilities	5,400
Pipeline and Storage, Gathering and Utility Segments
Recorded Unconditional Purchase Obligation [Line Items]
Contract commitments first year	86,300
Contract commitments second year	8,700
Contract commitments third year	6,500
Contract commitments fourth year	3,800
Contract commitments fifth year	3,800
Contract commitments thereafter	3,900
Exploration and Production
Recorded Unconditional Purchase Obligation [Line Items]
Contract commitments first year	218,600
Contract commitments second year	73,600
Contract commitments third year	$ 13,900