Investments In Unconsolidated Joint Ventures (150 Main Street, L.L.C.) (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Oct. 23, 2012
Schedule of Equity Method Investments [Line Items]
Maximum borrowing capacity	$ 600,000,000
JMP Eastchester, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Third party ownership percentage		26.25%
Hudson Valley Land Holdings, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Third party ownership percentage		47.50%
150 Main Street, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Percentage return on unrecovered capital	8.00%
Potential capital contribution	6,500,000
Potential additional interest	50.00%
Potential investment ownership percentage	63.25%
Holding and distribution pattern under operating agreement	The operating agreement of Eastchester provides, among other things, for the distribution of net operating cash flow to the members, as follows:to HVLH to the extent of its accrued but unpaid preferred return of eight percent on the unrecovered allocated land value, as defined; to the members, pro rata, to the extent of their respective accrued but unpaid return of eight percent on their unrecovered capital percentages; andto the members in accordance with their ownership percentages.
Eastchester Project [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of interest in venture		26.25%
Total project costs	46,000,000
Amount of project costs funded by members	8,500,000
Eastchester Project [Member] | 150 Main Street, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of units		108
Construction Loan [Member] | Eastchester Project [Member] | 150 Main Street, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Maximum borrowing capacity	$ 37,500,000