Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net Income (Loss) Available for Common Stock	$ (290,958)	$ (379,427)	$ 299,413
Other Comprehensive Income (Loss), Before Tax:
Decrease in the Funded Status of the Pension and Other Post-Retirement Benefit Plans	(21,378)	(31,538)	(8,280)
Reclassification Adjustment for Amortization of Prior Year Funded Status of the Pension and Other Post-Retirement Benefit Plans	10,068	9,217	9,203
Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	1,524	(3,234)	3,863
Unrealized Gain on Derivative Financial Instruments Arising During the Period	60,493	381,018	5,334
Reclassification Adjustment for Realized Gains on Securities Available for Sale in Net Income	(1,374)	(591)	(662)
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	(220,919)	(184,953)	17,647
Other Comprehensive Income (Loss), Before Tax	(171,586)	169,919	27,105
Income Tax Benefit Related to the Decrease in the Funded Status of the Pension and Other Post-Retirement Benefit Plans	(8,351)	(11,922)	(2,720)
Reclassification Adjustment for Income Tax Benefit Related to the Amortization of the Prior Year Funded Status of the Pension and Other Post-Retirement Benefit Plans	3,723	3,375	3,370
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	592	(1,195)	1,398
Income Tax Expense Related to Unrealized Gain on Derivative Financial Instruments Arising During the Period	18,648	160,872	529
Reclassification Adjustment for Income Tax Expense on Realized Gains from Securities Available for Sale in Net Income	(527)	(217)	(242)
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Derivative Financial Instruments in Net Income	(86,659)	(78,345)	9,515
Income Taxes - Net	(72,574)	72,568	11,850
Other Comprehensive Income (Loss)	(99,012)	97,351	15,255
Comprehensive Income (Loss)	$ (389,970)	$ (282,076)	$ 314,668