Investment in Unconsolidated Joint Ventures (Details 4) (Gramercy Capital Corp., USD $) Share data in Millions, unless otherwise specified	12 Months Ended					1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 First Gramercy lease sqft	Dec. 31, 2012 Second Gramercy lease sqft	Dec. 31, 2012 Third Gramercy lease sqft	Jun. 30, 2012 New lease sqft
Related party transactions
Shares held of Gramercy's common stock	0.7
Percentage of Gramercy's common stock owned	1.30%
Total investment in Gramercy	$ 2,200,000
Shares issued	2.5	2.1
Net proceeds generated	6,800,000
Realized gain on sale	4,900,000	4,500,000
Space leased (in square feet)			7,300	900	1,400	8,100
Term of lease			10 years
Annual lease rent for year one			249,000	35,300	67,300	345,000
Annual lease rent for year ten			315,000
Annual lease rent for year six				42,800	80,500
Annual lease rent for year three						$ 357,000