Noncash Investing and Financing Activities (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Other Significant Noncash Transactions [Line Items]
Debt Conversion, Converted Instrument, Amount	$ 0
Accrued dividends and distributions payable	47,546	43,547
Additions to real estate assets accrued but not yet paid	36,755	23,107
Noncash or Part Noncash Acquisition, Debt Assumed	40,368	177,296
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	2,800
Outlet Shoppes at Gettysburg [Member]
Other Significant Noncash Transactions [Line Items]
Debt Conversion, Converted Instrument, Amount		$ 4,522