Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net Income Available for Common Stock	$ 63,025	$ 59,714	$ 353,527	$ 237,906
Other Comprehensive Income (Loss), Before Tax:
Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	(121)	1,437	(843)	2,280
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	(37,452)	18,233	(55,534)	9,829
Reclassification Adjustment for Realized (Gains) Losses on Securities Available for Sale in Net Income	0	0	(430)	(741)
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	3,771	(18,452)	(5,577)	(59,641)
Other Comprehensive Income (Loss), Before Tax	(33,802)	1,218	(62,384)	(48,273)
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	42	532	(275)	832
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	(10,416)	7,592	(16,240)	3,892
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Securities Available for Sale in Net Income	0	0	(158)	(272)
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Derivative Financial Instruments in Net Income	1,208	(7,693)	(3,438)	(25,061)
Income Taxes – Net	(9,166)	431	(20,111)	(20,609)
Other Comprehensive Income (Loss)	(24,636)	787	(42,273)	(27,664)
Comprehensive Income	$ 38,389	$ 60,501	$ 311,254	$ 210,242