Shareholders' Equity Shareholders' Equity - Schedule of Forward Sales Executed (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares Available	3,335,995
Net Proceeds Available	$ 345,206
Forward Sales Equity Agreement, Maturing Quarter ended March 31, 2021
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares Available	1,281,578
Net Proceeds Available	$ 134,660
Forward Price	$ 105.07
Forward Sales Equity Agreement, Maturing Quarter ended June 30, 2021
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares Available		1,394,423
Net Proceeds Available	$ 142,388
Forward Price	$ 102.11
Forward Sales Equity Agreement, Maturing Quarter ended September 30, 2021
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares Available	659,994
Net Proceeds Available	$ 68,158
Forward Price	$ 103.27

The per share price of the Company's stock at which the contract holder of the freestanding contract has the right to purchase or sell the Company's stock at a future date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 5
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120519210&loc=d3e90205-114008

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=109262807&loc=d3e22047-110879

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- Definition

Current fair value of each cash settlement alternative for each freestanding forward contract.

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- Definition

Number of shares as a settlement alternative for each freestanding forward contract.

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