Shareholders' Equity Components (Details) - USD ($)	3 Months Ended	6 Months Ended
	Mar. 31, 2016	Mar. 31, 2016	Mar. 31, 2015	Mar. 28, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' equity, beginning balance		$ 3,194,797,000
Shareholders' equity, ending balance	$ 3,344,565,000	$ 3,344,565,000
Shareholders' Equity Other Disclosures [Abstract]
Share Repurchase Program - Shares Purchased		0	0
Debt and Equity Securities Authorized for Issuance				$ 2,500,000,000
ATM Equity Distribution Offering Price, Maximum Amount				$ 200,000,000
ATM Equity Distribution, Shares Issued	0
ATM Agent Commission on Proceeds, percentage				1.00%
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' equity, beginning balance		$ 4,949,000	$ 7,662,000
Other comprehensive income (loss) before reclassifications		(1,568,000)	(101,000)
Amounts reclassified from accumulated other comprehensive income		(79,000)	(4,000)
Net current-period other comprehensive income (loss)		(1,647,000)	(105,000)
Shareholders' equity, ending balance	$ 3,302,000	3,302,000	7,557,000
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Interest Rate Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' equity, beginning balance		(88,842,000)	(18,381,000)
Other comprehensive income (loss) before reclassifications		(49,008,000)	(84,824,000)
Amounts reclassified from accumulated other comprehensive income		173,000	368,000
Net current-period other comprehensive income (loss)		(48,835,000)	(84,456,000)
Shareholders' equity, ending balance	(137,677,000)	(137,677,000)	(102,837,000)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Commodity Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' equity, beginning balance		(25,437,000)	(1,674,000)
Other comprehensive income (loss) before reclassifications		(19,185,000)	(38,902,000)
Amounts reclassified from accumulated other comprehensive income		21,758,000	7,768,000
Net current-period other comprehensive income (loss)		2,573,000	(31,134,000)
Shareholders' equity, ending balance	(22,864,000)	(22,864,000)	(32,808,000)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' equity, beginning balance		(109,330,000)	(12,393,000)
Other comprehensive income (loss) before reclassifications		(69,761,000)	(123,827,000)
Amounts reclassified from accumulated other comprehensive income		21,852,000	8,132,000
Net current-period other comprehensive income (loss)		(47,909,000)	(115,695,000)
Shareholders' equity, ending balance	$ (157,239,000)	$ (157,239,000)	$ (128,088,000)