Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net Income Available for Common Stock	$ 167,328	$ 112,436	$ 299,720	$ 190,210
Other Comprehensive Income (Loss), Before Tax:
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	(641,606)	(34,373)	(478,474)	13,648
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	130,221	3,666	292,809	3,977
Other Post-Retirement Adjustment for Regulatory Proceeding	(7,351)	0	(7,351)	0
Other Comprehensive Income (Loss), Before Tax	(518,736)	(30,707)	(193,016)	17,625
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	(175,605)	(9,470)	(130,956)	3,760
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Derivative Financial Instruments in Net Income	35,641	1,010	80,141	1,096
Income Tax Expense (Benefit) Related to Other Post-Retirement Adjustment for Regulatory Proceeding	(1,544)	0	(1,544)	0
Income Taxes – Net	(141,508)	(8,460)	(52,359)	4,856
Other Comprehensive Income (Loss)	(377,228)	(22,247)	(140,657)	12,769
Comprehensive Income (Loss)	$ (209,900)	$ 90,189	$ 159,063	$ 202,979