Shareholders' Equity - Narrative (Details)		6 Months Ended
	Nov. 30, 2018 USD ($) Forward_seller shares	Mar. 31, 2020 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) $ / shares shares	Feb. 12, 2020 USD ($)	Feb. 11, 2020 USD ($)
Class of Stock [Line Items]
Value of shares authorized				$ 1,000,000,000.0
Forward contract indexed to issuer's equity, settlement alternatives, cash, at fair value		$ 418,580,000
Net proceeds from equity offering		258,047,000	$ 494,085,000
Number of forward sellers | Forward_seller	2
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
At-The-Market
Class of Stock [Line Items]
Forward sales equity agreement (in shares) | shares		1,890,857
Forward contract indexed to issuer's equity, settlement alternatives, cash, at fair value		$ 219,900,000
Stock issued during period, new issues (in shares) | shares		2,234,871
Value of shares available for issuance		$ 855,000,000
Net proceeds from equity offering		213,600,000
Common Stock Block Trade
Class of Stock [Line Items]
Stock issued during period, new issues (in shares) | shares	5,390,836
Net proceeds from equity offering	$ 494,100,000
Gross proceeds from equity offering	500,000,000
Forward Sales Equity Agreements
Class of Stock [Line Items]
Forward contract indexed to issuer's equity, settlement alternatives, cash, at fair value	$ 247,500,000	$ 418,600,000
Stock issued during period, new issues (in shares) | shares	2,668,464	485,189	1,670,509
Net proceeds from equity offering		$ 44,400,000
Forward sales equity agreement, forward rate per share | $ / shares		$ 110.13	$ 95.46