Unconsolidated Real Estate Joint Ventures (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended									0 Months Ended	12 Months Ended				12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Atlantic-EPR II [Member]	Dec. 31, 2012 Atlantic-EPR II [Member]	Dec. 31, 2011 Atlantic-EPR II [Member]	Dec. 31, 2013 Atlantic-EPR I [Member]	Dec. 31, 2012 Atlantic-EPR I [Member]	Dec. 31, 2011 Atlantic-EPR I [Member]	Oct. 09, 2013 Atlantic-EPR I and II [Member]	Dec. 31, 2013 Atlantic-EPR I and II [Member]	Dec. 31, 2012 Atlantic-EPR I and II [Member]	Dec. 31, 2011 Atlantic-EPR I and II [Member]	Oct. 08, 2013 Atlantic-EPR I and II [Member]	Dec. 31, 2013 Theatre Project China [Member]	Dec. 31, 2012 Theatre Project China [Member]	Dec. 31, 2011 Theatre Project China [Member]
Number of unconsolidated joint ventures																2	3	3
Payments to Acquire Productive Assets			$ 123,497,000	$ 73,188,000	$ 53,175,000							$ 18,600,000
Additional amount contributed in equity						424,000	490,000	258,000	1,200,000	1,300,000	2,500,000
Mortgage Loans on Real Estate, New Mortgage Loans												33,100,000
Gain on previously held equity interest			4,853,000	0	0
Gain on sale or acquisition, net	282,000	1,200,000	3,017,000	0	0								3,200,000
Income from investments in unconsolidated real estate joint venture			1,398,000	1,025,000	2,847,000								505,000	536,000	2,800,000
Maximum exchange of ownership interest per year			10.00%
Additional ownership interest in unconsolidated real estate joint ventures						3.20%	3.80%	2.00%	6.40%	6.00%	11.30%
Investment in joint ventures																	5,300,000	4,700,000
Loss from investments in unconsolidated real estate joint venture																	893,000	489,000	42,000
Distributions from joint ventures			$ 985,000	$ 1,046,000	$ 2,848,000								$ 646,000	$ 1,000,000	$ 2,800,000		$ 339,000