Commitments and Contingencies - Contractual Obligations (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jan. 31, 2018
Fashion District Philadelphia
Other Commitments [Line Items]
Unaccrued contractual obligation and other commitments	$ 61.0
Ownership percentage		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	$ 118.5