Noncash Investing and Financing Activities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Supplemental Cash Flow Information [Line Items]
Accrued dividends and distributions payable	$ 54,490	$ 50,534
Additions to real estate assets accrued but not yet paid	10,301	14,256
Decrease in real estate assets	0	(22,605)
Decrease in mortgage and other indebtedness	0	68,169
Decrease in operating assets and liabilities	0	(1,655)
Eastgate Crossing
Supplemental Cash Flow Information [Line Items]
Assumption of mortgage loan from sale of EastGate Crossing	14,570	0
Lakeshore Mall
Supplemental Cash Flow Information [Line Items]
Note receivable from sale of Lakeshore Mall	$ 0	$ 10,000