Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income (Loss) Available for Common Stock	$ 89,284	$ (147,687)	$ 178,191	$ (336,796)
Other Comprehensive Income (Loss), Before Tax:
Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	1,726	(4)	843	(642)
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	44,097	33,768	(8,404)	99,139
Reclassification Adjustment for Realized (Gains) Losses on Securities Available for Sale in Net Income	0	(388)	(741)	(388)
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	(10,472)	(61,235)	(41,189)	(118,405)
Other Comprehensive Income (Loss), Before Tax	35,351	(27,859)	(49,491)	(20,296)
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	645	(16)	300	(207)
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	18,352	14,190	(3,699)	34,866
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Securities Available for Sale in Net Income	0	(163)	(272)	(163)
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Derivative Financial Instruments in Net Income	(4,414)	(25,600)	(17,369)	(43,606)
Income Taxes – Net	14,583	(11,589)	(21,040)	(9,110)
Other Comprehensive Income (Loss)	20,768	(16,270)	(28,451)	(11,186)
Comprehensive Income (Loss)	$ 110,052	$ (163,957)	$ 149,740	$ (347,982)