Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income Available for Common Stock	$ 102,660	$ 198,654
Other Comprehensive Income (Loss), Before Tax:
Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	0	(44)
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	44,518	(5,499)
Reclassification Adjustment for Realized (Gains) Losses on Securities Available for Sale in Net Income	0	(430)
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	20,517	(12,548)
Reclassification Adjustment for the Cumulative Effect of Adoption of Authoritative Guidance for Financial Assets and Liabilities to Earnings Reinvested in the Business	(11,738)	0
Other Comprehensive Income (Loss), Before Tax	53,297	(18,521)
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	0	(65)
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	12,744	(2,305)
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Securities Available for Sale in Net Income	0	(158)
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Derivative Financial Instruments in Net Income	5,794	(5,197)
Reclassification Adjustment for Income Tax Benefit (Expense) on the Cumulative Effect of Adoption of Authoritative Guidance for Financial Assets and Liabilities to Earnings Reinvested in the Business	(4,301)	0
Income Taxes – Net	14,237	(7,725)
Other Comprehensive Income (Loss)	39,060	(10,796)
Comprehensive Income	$ 141,720	$ 187,858