Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement of Comprehensive Income [Abstract]
Net Income Available for Common Stock	$ 108,158	$ 86,475	$ 407,879	$ 276,685
Other Comprehensive Income (Loss), Before Tax:
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	(200,084)	(201,498)	(678,558)	(187,850)
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	298,371	13,129	591,180	17,106
Other Post-Retirement Adjustment for Regulatory Proceeding	0	0	(7,351)	0
Other Comprehensive Income (Loss), Before Tax	98,287	(188,369)	(94,729)	(170,744)
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	(54,762)	(55,512)	(185,717)	(51,752)
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Derivative Financial Instruments in Net Income	81,663	3,617	161,803	4,713
Income Tax Expense (Benefit) Related to Other Post-Retirement Adjustment for Regulatory Proceeding	0	0	(1,544)	0
Income Taxes – Net	26,901	(51,895)	(25,458)	(47,039)
Other Comprehensive Income (Loss)	71,386	(136,474)	(69,271)	(123,705)
Comprehensive Income (Loss)	$ 179,544	$ (49,999)	$ 338,608	$ 152,980