Details of Selected Consolidated Balance Sheet Captions - Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Customer credit balances and deposits	$ 56,016	$ 49,722
Accrued employee costs	47,661	50,517
Deferred gas costs	28,834	52,553
Operating lease liabilities (See Note 6)	38,644	37,688
Accrued interest	59,542	55,164
Liabilities from risk management activities	3,000	5,269
Taxes payable	189,239	160,986
Pension and postretirement liabilities	9,721	4,863
Regulatory cost of removal obligation	80,676	72,823
APT annual adjustment mechanism	18,034	22,694
Regulatory excess deferred taxes (See Note 14)	159,808	155,857
Other	28,982	18,545
Total	$ 720,157	$ 686,681