Shareholders' Equity - Schedule of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Oct. 01, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	$ 5,750,223	$ 4,769,951
Other comprehensive loss before reclassifications	(1)	(22,716)
Amounts reclassified from accumulated other comprehensive income	1,053	458
Net current-period other comprehensive income (loss)	1,052	(22,258)
Shareholders' equity, ending balance	6,127,775	5,348,195
Cumulative effect of accounting change		(8,210)
Available- for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	132	8,124
Other comprehensive loss before reclassifications	(1)	0
Amounts reclassified from accumulated other comprehensive income	0	0
Net current-period other comprehensive income (loss)	(1)	0
Shareholders' equity, ending balance	131	(86)
Cumulative effect of accounting change		(8,210)
Interest Rate Agreement Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	(114,715)	(91,771)
Other comprehensive loss before reclassifications	0	(22,716)
Amounts reclassified from accumulated other comprehensive income	1,053	458
Net current-period other comprehensive income (loss)	1,053	(22,258)
Shareholders' equity, ending balance	(113,662)	(114,029)
Cumulative effect of accounting change		0
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	(114,583)	(83,647)
Net current-period other comprehensive income (loss)	1,052	(22,258)
Shareholders' equity, ending balance	$ (113,531)	$ (114,115)
Cumulative effect of accounting change			$ (8,210)

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

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- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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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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