Cash Flow Disclosures and Non-Cash Investing and Financing Activities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Interest Costs Capitalized	$ 24,569	$ 18,844
Interest Paid, Net	43,700	70,500
Income Taxes Paid, Net	$ 2,100	9,900
Issuance of partnership units in connection with the purchase of the U.S. headquarters building		91
Noncash or Part Noncash Acquisition, Debt Assumed including Unamortized Premium		18,215
Capital Expenditures Incurred but Not yet Paid	$ 75,880	53,018
The Mall of San Juan [Member]
Recapitalization of The Mall of San Juan Joint Venture	$ 9,296
SPG Units [Member]
Partnership Units Received as Part of Consideration in Connection with Sale of Equity Method Investment and Other Assets, Book Value		$ 77,711