Shareholders' Equity - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Oct. 01, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	$ 4,769,951	$ 3,898,666
Net current-period other comprehensive loss	(22,258)	(1,062)
Cummulative effect on accounting change, on equity or net assets			$ 8,200
Shareholders' equity, ending balance	5,348,195	4,563,620
Available- for-Sale Securities(1)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	8,124	7,048
Other comprehensive loss before reclassifications	0	(107)
Amounts reclassified from accumulated other comprehensive income	0	0
Net current-period other comprehensive loss	0	(107)
Cummulative effect on accounting change, on equity or net assets			(8,210)
Shareholders' equity, ending balance	(86)	6,941
Cash Flow Hedges \| Interest rate agreements
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	(91,771)	(112,302)
Other comprehensive loss before reclassifications	(22,716)	(1,332)
Amounts reclassified from accumulated other comprehensive income	458	377
Net current-period other comprehensive loss	(22,258)	(955)
Cummulative effect on accounting change, on equity or net assets			$ 0
Shareholders' equity, ending balance	(114,029)	(113,257)
Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	(83,647)	(105,254)
Other comprehensive loss before reclassifications	(22,716)	(1,439)
Amounts reclassified from accumulated other comprehensive income	458	377
Net current-period other comprehensive loss	(22,258)	(1,062)
Cummulative effect on accounting change, on equity or net assets	(8,210)
Shareholders' equity, ending balance	$ (114,115)	$ (106,316)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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