Marketable Securities (Details) - Macerich interest - USD ($)	1 Months Ended	12 Months Ended
	Oct. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Investment holdings
Macerich Common Shares		535,265	535,265
Economic basis per share (in dollars per share)		$ 56.05
GAAP Cost		$ 30,000,000
Fair Value		$ 37,918,000	$ 43,191,000
Closing share price (in dollars per share)		$ 70.84	$ 80.69
Unrealized gain (loss)		$ (5,273,000)	$ (1,455,000)
Investment Income Dividend	$ 2,141,000		$ 2,141,000