Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
Net Income Available for Common Stock	$ 299,413	$ 260,001	$ 220,077
Other Comprehensive Income (Loss), Before Tax:
Increase (Decrease) in the Funded Status of the Pension and Other Post-Retirement Benefit Plans	(8,280)	55,940	(27,552)
Reclassification Adjustment for Amortization of Prior Year Funded Status of the Pension and Other Post-Retirement Benefit Plans	9,203	15,282	10,270
Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	3,863	5,041	3,545
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	5,334	91,790	(7,248)
Reclassification Adjustment for Realized (Gains) Losses on Securities Available for Sale in Net Income	(662)	0	0
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	17,647	(36,029)	(65,691)
Other Comprehensive Income (Loss), Before Tax	27,105	132,024	(86,676)
Income Tax Expense (Benefit) Related to the Increase (Decrease) in the Funded Status of the Pension and Other Post-Retirement Benefit Plans	(2,720)	21,304	(10,144)
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	3,370	5,650	3,836
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	1,398	1,847	1,311
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	529	38,236	(8,244)
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Securities Available for Sale in Net Income	(242)	0	0
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) on Derivative Financial Instruments in Net Income	9,515	(14,799)	(22,114)
Income Taxes - Net	11,850	52,238	(35,355)
Other Comprehensive Income (Loss)	15,255	79,786	(51,321)
Comprehensive Income	$ 314,668	$ 339,787	$ 168,756