Consolidated Statements Of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net Income Available for Common Stock	$ 16,669us-gaap_NetIncomeLoss	$ 95,211us-gaap_NetIncomeLoss	$ 101,409us-gaap_NetIncomeLoss	$ 177,463us-gaap_NetIncomeLoss
Other Comprehensive Income (Loss), Before Tax:
Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	265	622	(147)	3,120
Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	61,165	(67,461)	304,994	(64,682)
Reclassification Adjustment for Realized (Gains) Losses on Derivative Financial Instruments in Net Income	(54,130)	26,640	(78,395)	16,457
Other Comprehensive Income (Loss), Before Tax	7,300	(40,199)	226,452	(45,105)
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Securities Available for Sale Arising During the Period	99	231	(61)	1,156
Income Tax Expense (Benefit) Related to Unrealized Gain (Loss) on Derivative Financial Instruments Arising During the Period	25,902	(28,583)	128,851	(27,312)
Reclassification Adjustment for Income Tax Benefit (Expense) on Realized Losses (Gains) from Derivative Financial Instruments in Net Income	(22,917)	11,170	(33,006)	6,872
Income Taxes – Net	3,084us-gaap_OtherComprehensiveIncomeLossTax	(17,182)us-gaap_OtherComprehensiveIncomeLossTax	95,784us-gaap_OtherComprehensiveIncomeLossTax	(19,284)us-gaap_OtherComprehensiveIncomeLossTax
Other Comprehensive Income (Loss)	4,216	(23,017)	130,668	(25,821)
Comprehensive Income	$ 20,885	$ 72,194	$ 232,077	$ 151,642

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

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