Properties Held for Sale and Dispositions (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Revenues
Rental revenue	$ 5,076,000	$ 8,804,000
Escalation and reimbursement revenues	821,000	1,196,000
Other income	0	8,000
Total revenues	5,897,000	10,008,000
Operating expenses	884,000	2,467,000
Real estate taxes	1,019,000	1,254,000
Ground rent	2,196,000	2,863,000
Interest expense, net of interest income	659,000	561,000
Depreciation and amortization	433,000	2,067,000
Total expenses	5,191,000	9,212,000
Net income from discontinued operations	706,000	796,000
Subsequent Event | 673 First Avenue
Property Dispositions and Assets Held for Sale
Proceeds from sale of other productive assets	$ 145,000,000