Shareholders' Equity - Narrative (Details) - USD ($)		12 Months Ended
	Nov. 30, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Oct. 01, 2020	Feb. 12, 2020	Feb. 11, 2020
Class of Stock [Line Items]
Net proceeds from equity offering		$ 624,302,000	$ 694,103,000	$ 395,092,000
Forward sales equity agreement, settlement in cash		345,206,000
Shelf Registration Statement
Class of Stock [Line Items]
Debt and equity securities authorized for issuance							$ 4,000,000,000.0
Debt and equity securities authorized for issuance value remaining		3,000,000,000.0			$ 2,400,000,000
At-The-Market
Class of Stock [Line Items]
Value of shares authorized for issuance						$ 1,000,000,000.0
Value of shares available for issuance		$ 552,000,000
Shares issued		5,616,727	2,183,275
Net proceeds from equity offering		$ 581,500,000	$ 200,000,000.0
Forward sales equity agreement, settlement in cash		$ 523,200,000
Forward sales equity agreement, shares		4,808,051	4,144,671
Common Stock Block Trade
Class of Stock [Line Items]
Shares issued	5,390,836
Proceeds from issuance of common stock gross	$ 500,000,000
Net proceeds from equity offering	494,100,000
Forward sales equity agreement, settlement in cash	$ 247,500,000
Forward sales equity agreement, shares	2,668,464
Forward Sales Equity Agreements
Class of Stock [Line Items]
Shares issued		485,189
Net proceeds from equity offering		$ 44,400,000
Forward sales equity agreement, settlement in cash		$ 345,200,000	$ 425,000,000.0
Forward sales equity agreement, forward rate per share		$ 103.48
Senior Notes | Unsecured 1.50% Senior Notes, Due 2031 | Subsequent Event
Class of Stock [Line Items]
Debt face amount					$ 600,000,000