Investments in and Advances to Unconsolidated Joint Ventures (Investments in and Advances to Unconsolidated Joint Ventures) (Details) (USD $) In Thousands, unless otherwise specified						9 Months Ended	12 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2012 property		Dec. 31, 2011		Jan. 31, 2011 property	Sep. 30, 2012 GRI-EQY I, LLC [Member]	Dec. 31, 2011 GRI-EQY I, LLC [Member]	Sep. 30, 2012 Talega Village Center JV, LLC [Member]	Sep. 30, 2012 Equity One JV Portfolio, LLC (NYCRF) [Member]	Dec. 31, 2011 Equity One JV Portfolio, LLC (NYCRF) [Member]	Sep. 30, 2012 Vestar [Member]	Sep. 30, 2012 Georgia, South Carolina & Florida [Member] GRI-EQY I, LLC [Member] property		Dec. 31, 2011 Georgia, South Carolina & Florida [Member] GRI-EQY I, LLC [Member]		Sep. 30, 2012 Florida [Member] G&I Investment South Florida Portfolio, LLC [Member] property		Dec. 31, 2011 Florida [Member] G&I Investment South Florida Portfolio, LLC [Member]		Sep. 30, 2012 New York [Member] Madison 2260, Realty, LLC [Member] property		Dec. 31, 2011 New York [Member] Madison 2260, Realty, LLC [Member]		Sep. 30, 2012 New York [Member] Madison 1235, Realty, LLC [Member] property		Dec. 31, 2011 New York [Member] Madison 1235, Realty, LLC [Member]		Sep. 30, 2012 California [Member] Talega Village Center JV, LLC [Member] property		Dec. 31, 2011 California [Member] Talega Village Center JV, LLC [Member]		Sep. 30, 2012 California [Member] Vernola Marketplace JV, LLC [Member] property		Dec. 31, 2011 California [Member] Vernola Marketplace JV, LLC [Member]		Sep. 30, 2012 California [Member] Parnassus Heights Medical Center [Member] property		Dec. 31, 2011 California [Member] Parnassus Heights Medical Center [Member]		Sep. 30, 2012 Florida & Massachusetts [Member] Equity One JV Portfolio, LLC (NYCRF) [Member] property		Dec. 31, 2011 Florida & Massachusetts [Member] Equity One JV Portfolio, LLC (NYCRF) [Member]
Schedule of Equity Method Investments [Line Items]
Number of properties	167				13							10	[1],[2]			3	[1]			1	[1]			1	[1]			1	[1],[3]			1	[1],[3]			1	[1]			3	[1],[4]
Ownership interests in properties through joint ventures												10.00%	[1],[2]			20.00%	[1]			8.60%	[1]			20.10%	[1]			50.50%	[1],[3]			50.50%	[1],[3]			50.00%	[1]			30.00%	[1],[4]
Investments in unconsolidated joint ventures, Investment Balance	$ 60,946	[1]	$ 49,127	[1]								$ 8,355	[1],[2]	$ 7,705	[1],[2]	$ 3,504	[1]	$ 3,215	[1]	$ 634	[1]	$ 1,066	[1]	$ 1,000	[1]	$ 1,000	[1]	$ 3,041	[1],[3]	$ 3,620	[1],[3]	$ 7,180	[1],[3]	$ 7,433	[1],[3]	$ 20,459	[1]	$ 13,695	[1]	$ 16,773	[1],[4]	$ 11,393	[1],[4]
Advances to unconsolidated joint ventures, Investment Balance	503	[1]	1,031	[1]
Investments in and advances to unconsolidated joint ventures	61,449	[1]	50,158	[1]
Net of deferred gains associated with the disposition of assets						$ 3,300	$ 3,300		$ 404	$ 404
Effective interest rate, noncontrolling interest								48.00%			5.00%

[1] With the exception of the Madison 2260 Realty LLC and Madison 1235 Realty LLC joint ventures, which are accounted for under the cost method, all unconsolidated joint ventures are accounted for under the equity method.

[2] The investment balance as of September 30, 2012 and December 31, 2011 is presented net of deferred gains of $3.3 million for both periods associated with the disposition of assets by us to the joint venture.

[3] Our effective interest is 48% when considering the 5% noncontrolling interest held by Vestar Development Company.

[4] The investment balance as of September 30, 2012 and December 31, 2011 is presented net of a deferred gain of approximately $404,000 for both periods associated with the disposition of assets by us to the joint venture in 2011.