Marketable Securities (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) specialdividends $ / shares shares	Dec. 31, 2015 USD ($) specialdividends $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares
Investment Holdings [Line Items]
Fair Value		$ 43,191	$ 43,191	$ 44,646
Macerich interest [Member]
Investment Holdings [Line Items]
Macerich Common Shares | shares		535,265	535,265	535,265
Economic basis per share (in dollars per share) | $ / shares		$ 56.05	$ 56.05
GAAP Cost		$ 30,000	$ 30,000
Fair Value		$ 43,191	$ 43,191	$ 44,646
Closing share price (in dollars per share) | $ / shares		$ 80.69	$ 80.69	$ 83.41
Unrealized gain (loss)			$ (1,455)	$ 13,124
Number Of Special Dividends | specialdividends		2	2
Special Dividends Per Share | $ / shares		$ 2
Investment Income Dividend	$ 2,141