Noncontrolling Interests: (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Aug. 20, 2014	Aug. 17, 2012
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Limited partnership interest of the operating partnership (as a percent)	6.00%	6.00%
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Number of trading days used to calculate redemption value (in days)	10 days
Redemption value of outstanding OP Units not owned by the Company	$ 815,341	$ 877,184
The Macerich Partnership, L.P.
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Ownership interest in operating partnership (as a percent)	94.00%	94.00%