Debt - Revolving Credit Facility (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Line of Credit Facility [Line Items]
Amount outstanding	$ 1,685,200,000	$ 2,127,300,000
Unsecured Revolving Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Borrowing capacity	500,000,000.0
Increase amount of borrowings, subject to lenders' approval	200,000,000.0
Amount outstanding	$ 0