Shareholders' Equity - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Oct. 01, 2021	Jun. 29, 2021	Oct. 01, 2020
Class of Stock [Line Items]
Net proceeds from equity offering	$ 606,667,000	$ 624,302,000	$ 694,103,000
Forward sales equity agreement, settlement in cash	301,984,000
Shelf Registration Statement
Class of Stock [Line Items]
Debt and equity securities authorized for issuance					$ 5,000,000,000
Debt and equity securities authorized for issuance value remaining	4,000,000,000
At-The-Market
Class of Stock [Line Items]
Value of shares authorized for issuance					$ 1,000,000,000
Value of shares available for issuance	$ 760,000,000
Shares issued	6,130,875
Net proceeds from equity offering	$ 606,700,000
Forward sales equity agreement, settlement in cash	$ 578,400,000
Forward sales equity agreement, shares	5,866,604
Subsequent Event | Shelf Registration Statement
Class of Stock [Line Items]
Debt and equity securities authorized for issuance value remaining				$ 3,400,000,000
Senior Notes | Unsecured 1.50% Senior Notes, Due 2031
Class of Stock [Line Items]
Debt face amount						$ 600,000,000
Senior Notes | Unsecured 1.50% Senior Notes, Due 2031 | Subsequent Event
Class of Stock [Line Items]
Debt face amount				$ 600,000,000