Winter Storm Uri (Details) - USD ($) $ in Thousands					1 Months Ended	6 Months Ended		7 Months Ended
	Mar. 23, 2023	Mar. 09, 2023	Mar. 03, 2023	Oct. 25, 2022	Feb. 28, 2021	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Sep. 30, 2022	Mar. 31, 2021
Unusual or Infrequent Item, or Both [Line Items]
Aggregate natural gas purchases					$ 2,300,000
Repayment of senior notes						$ 2,200,000	$ 200,000
Regulatory assets						513,931		$ 513,931	$ 2,605,372
Winter Storm Uri incremental costs
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets						121,493		121,493	$ 2,109,454
Winter Storm Uri incremental costs | Winter Storm Uri | Kansas
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets						$ 89,100		89,100
Winter Storm Uri incremental costs | Winter Storm Uri | Texas
Unusual or Infrequent Item, or Both [Line Items]
Regulatory asset, deferred costs								$ 32,400
Extraordinary Gas Cost | Winter Storm Uri | Kansas
Unusual or Infrequent Item, or Both [Line Items]
Regulatory asset, authorized				$ 118,500
Regulatory asset, amortization period				12 years
Extraordinary Gas Cost | Winter Storm Uri | Texas
Unusual or Infrequent Item, or Both [Line Items]
Regulatory asset, authorized	$ 3,500,000
Proceeds from customer rate relief bonds	2,020,000
Regulatory asset, relieved	$ 2,020,000
Extraordinary Gas Cost | Winter Storm Uri | Texas | Minimum
Unusual or Infrequent Item, or Both [Line Items]
Regulatory asset, maturity period	12 years
Extraordinary Gas Cost | Winter Storm Uri | Texas | Maximum
Unusual or Infrequent Item, or Both [Line Items]
Regulatory asset, maturity period	18 years
Senior Notes
Unusual or Infrequent Item, or Both [Line Items]
Debt instrument, face amount										$ 2,200,000
Repayment of senior notes			$ 2,200,000
Unsecured Debt | Line of Credit
Unusual or Infrequent Item, or Both [Line Items]
Repayment of senior notes		$ 1,100,000
Unsecured Senior Term Loan Due 2023 | Unsecured Debt | Line of Credit
Unusual or Infrequent Item, or Both [Line Items]
Debt instrument, face amount			$ 2,020,000