Summary of Significant Accounting Policies Depreciation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Sep. 30, 2021
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 459	$ 347	$ 1,400	$ 1,000
Increase due to new depreciation rates
Property, Plant and Equipment [Line Items]
Depreciation expense			$ 309
Nuclear Plant
Property, Plant and Equipment [Line Items]
Public utilities, property, plant and equipment, disclosure of composite depreciation rate for plants of service			2.72%		2.38%
Fossil Fuel Plant
Property, Plant and Equipment [Line Items]
Public utilities, property, plant and equipment, disclosure of composite depreciation rate for plants of service			3.98%		1.95%
Hydro Plant
Property, Plant and Equipment [Line Items]
Public utilities, property, plant and equipment, disclosure of composite depreciation rate for plants of service			1.95%		1.60%
Natural Gas Processing Plant
Property, Plant and Equipment [Line Items]
Public utilities, property, plant and equipment, disclosure of composite depreciation rate for plants of service			3.45%		2.98%
Electric Transmission
Property, Plant and Equipment [Line Items]
Public utilities, property, plant and equipment, disclosure of composite depreciation rate for plants of service			1.45%		1.34%
Other Plant in Service
Property, Plant and Equipment [Line Items]
Public utilities, property, plant and equipment, disclosure of composite depreciation rate for plants of service			3.21%		7.12%