Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net Income (Loss) Available for Common Stock	$ 59,714	$ 8,286	$ 237,906	$ (328,510)
Other Comprehensive Income (Loss), Before Tax:
Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	1,437	376	2,280	(266)
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	18,233	(70,363)	9,829	28,777
Reclassification Adjustment for Realized (Gains) Losses on Securities Available for Sale in Net Income	0	0	(741)	(388)
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	(18,452)	(58,373)	(59,641)	(176,779)
Other Comprehensive Income (Loss), Before Tax	1,218	(128,360)	(48,273)	(148,656)
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	532	122	832	(85)
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	7,592	(29,521)	3,892	5,345
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Securities Available for Sale in Net Income	0	0	(272)	(163)
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Derivative Financial Instruments in Net Income	(7,693)	(24,514)	(25,061)	(68,120)
Income Taxes – Net	431	(53,913)	(20,609)	(63,023)
Other Comprehensive Income (Loss)	787	(74,447)	(27,664)	(85,633)
Comprehensive Income (Loss)	$ 60,501	$ (66,161)	$ 210,242	$ (414,143)