Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Consolidated Statements Of Comprehensive Income [Abstract]
Net Income Available for Common Stock	$ 85,720	$ 67,392	$ 153,664	$ 128,091
Other Comprehensive Income (Loss), Before Tax:
Unrealized Gain on Securities Available for Sale Arising During the Period	1,983	3,116	2,773	3,828
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	(47,350)	14,498	(12,001)	16,653
Reclassification Adjustment for Realized Gains on Derivative Financial Instruments in Net Income	(10,503)	(16,185)	(22,088)	(28,050)
Other Comprehensive Income (Loss), Before Tax	(55,870)	1,429	(31,316)	(7,569)
Income Tax Expense Related to Unrealized Gain On Securities Available for Sale Arising During the Period	741	1,161	1,037	1,424
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	(19,813)	840	(5,076)	1,657
Reclassification Adjustment for Income Tax Expense on Realized Gains from Derivative Financial Instruments In Net Income	(4,419)	(1,816)	(9,274)	(6,460)
Income Taxes - Net	(23,491)	185	(13,313)	(3,379)
Other Comprehensive Income (Loss)	(32,379)	1,244	(18,003)	(4,190)
Comprehensive Income	$ 53,341	$ 68,636	$ 135,661	$ 123,901