Winter Storm Uri (Details) - USD ($) $ in Thousands	1 Months Ended
	Feb. 28, 2021	Sep. 30, 2021	Sep. 14, 2021	Jul. 30, 2021	Mar. 09, 2021	Sep. 30, 2020
Unusual or Infrequent Item, or Both [Line Items]
Aggregate natural gas purchases	$ 2,300,000
Regulatory assets		$ 2,521,441				$ 414,641
Capitalized for rate making purposes		2,800
Winter Storm Uri incremental costs
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets		2,100,728				$ 0
Winter Storm Uri incremental costs | Winter Storm Uri
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets		2,100,000
Winter Storm Uri incremental costs | Kansas | Winter Storm Uri
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets		89,000
Winter Storm Uri incremental costs | Texas | Winter Storm Uri
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets		$ 2,011,700
Extraordinary Gas Cost | Winter Storm Uri
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets			$ 94,100	$ 2,000,000
Senior Notes Due 2023
Unusual or Infrequent Item, or Both [Line Items]
Debt instrument, face amount					$ 2,200,000
Administrative costs					$ 600