Acquisitions (Summary of Income Producing Property Acquisition Activity) (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended		6 Months Ended
	Dec. 31, 2011 sqft	Jan. 31, 2011 sqft	Jun. 30, 2012 sqft
Business Acquisition [Line Items]
Square Feet	3,900,000	2,600,000	16,800,000
Purchase Price			$ 161,250
Bronx [Member] | Broadway Plaza - land parcel [Member]
Business Acquisition [Line Items]
Date Purchased			Jun. 08, 2012
Acres			1.83	[1]
Purchase Price			7,500
San Francisco [Member] | Potrero Center [Member]
Business Acquisition [Line Items]
Date Purchased			Mar. 01, 2012	[2]
Square Feet			226,699	[2]
Purchase Price			110,750	[2]
Westport [Member] | Compo Acres Shopping Center [Member]
Business Acquisition [Line Items]
Date Purchased			Mar. 01, 2012	[2]
Square Feet			43,107	[2]
Purchase Price			30,300	[2]
Darien [Member] | Post Road Plaza [Member]
Business Acquisition [Line Items]
Date Purchased			Mar. 01, 2012	[2]
Square Feet			20,005	[2]
Purchase Price			$ 12,700	[2]

[1] In acres.

[2] The purchase price has been preliminarily allocated to real estate assets acquired and liabilities, as applicable, assumed in accordance with our accounting policies for business combinations. The purchase price and related accounting will be finalized after our valuation studies are complete.