Marketable Securities (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investment Holdings [Line Items]
Fair Value	$ 41,119	$ 44,646
Macerich interest [Member]
Investment Holdings [Line Items]
Macerich Common Shares	535,265	535,265
Economic basis per share (in dollars per share)	$ 56.05
GAAP Cost	$ 30,000
Fair Value	$ 41,119	$ 44,646
Closing share price (in dollars per share)	$ 76.82	$ 83.41