Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net Income (Loss) Available for Common Stock	$ (379,427)	$ 299,413	$ 260,001
Other Comprehensive Income (Loss), Before Tax:
Increase (Decrease) in the Funded Status of the Pension and Other Post-Retirement Benefit Plans	(31,538)	(8,280)	55,940
Reclassification Adjustment for Amortization of Prior Year Funded Status of the Pension and Other Post-Retirement Benefit Plans	9,217	9,203	15,282
Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	(3,234)	3,863	5,041
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	381,018	5,334	91,790
Reclassification Adjustment for Realized (Gains) Losses on Securities Available for Sale in Net Income	(591)	(662)	0
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	(184,953)	17,647	(36,029)
Other Comprehensive Income (Loss), Before Tax	169,919	27,105	132,024
Income Tax Expense (Benefit) Related to the Increase (Decrease) in the Funded Status of the Pension and Other Post-Retirement Benefit Plans	(11,922)	(2,720)	21,304
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	3,375	3,370	5,650
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	(1,195)	1,398	1,847
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	160,872	529	38,236
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Securities Available for Sale in Net Income	(217)	(242)	0
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) on Derivative Financial Instruments in Net Income	(78,345)	9,515	(14,799)
Income Taxes - Net	72,568	11,850	52,238
Other Comprehensive Income	97,351	15,255	79,786
Comprehensive Income (Loss)	$ (282,076)	$ 314,668	$ 339,787