Commitments and Contingencies - Contractual Obligations (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Jan. 31, 2018
Fashion District Philadelphia
Other Commitments [Line Items]
Unaccrued contractual obligation and other commitments	$ 14.1
Percentage of contractual obligation	100.00%
Ownership percentage	50.00%	50.00%
Fashion District Philadelphia | Macerich | Corporate Joint Venture
Other Commitments [Line Items]
Unaccrued contractual obligation and other commitments	$ 300.0
Contractual obligation, period after commencement	48 months
Construction in Progress
Other Commitments [Line Items]
Unaccrued contractual obligation and other commitments	$ 27.9