Consolidated Statements Of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Statement of Comprehensive Income [Abstract]
Net Income Available for Common Stock	$ 95,211	$ 85,720	$ 177,463	$ 153,664
Other Comprehensive Income (Loss), Before Tax:
Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	622	1,983	3,120	2,773
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	(67,461)	(47,350)	(64,682)	(12,001)
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	26,640	(10,503)	16,457	(22,088)
Other Comprehensive Income (Loss), Before Tax	(40,199)	(55,870)	(45,105)	(31,316)
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	231	741	1,156	1,037
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	(28,583)	(19,813)	(27,312)	(5,076)
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Derivative Financial Instruments in Net Income	11,170	(4,419)	6,872	(9,274)
Income Taxes – Net	(17,182)	(23,491)	(19,284)	(13,313)
Other Comprehensive Income (Loss)	(23,017)	(32,379)	(25,821)	(18,003)
Comprehensive Income	$ 72,194	$ 53,341	$ 151,642	$ 135,661