Fair Value Disclosures (Details) - Fair Value, Inputs, Level 2 [Member] - SPG Units [Member] - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Units of Partnership Interest, Amount	340,124	340,124
Partnership Units, Fair Value at Reporting Date	$ 58,500	$ 60,400
Partnership Units, Book Value at Reporting Date	$ 44,792	$ 44,792