Schedule III - Real Estate and Accumulated Depreciation (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Real Estate Properties [Line Items]
Description	Land, building and building improvements and equipment situated at One Grand Central Place, 60 East 42nd Street and 301 Madison Avenue, New York, N.Y. (fully depreciated)	Land, building and building improvements and equipment situated at One Grand Central Place, 60 East 42nd Street and 301 Madison Avenue, New York, N.Y. (fully depreciated)
Encumbrances
Prudential Insurance Company at December 31	$ 89,109,449	$ 91,478,304
Initial cost to company
Land	7,240,000	7,240,000
Building	16,960,000	16,960,000
Cost capitalized subsequent to acquisition
Building improvements and equipment	76,819,488	78,308,199
Carrying costs
Gross amount at which carried at close of period
Land	7,240,000	7,240,000
Building, building improvements and equipment	93,779,488	91,268,199
Total	101,019,488	98,508,199
Accumulated depreciation	33,403,883	32,107,921
Date of construction	1930	1930
Date acquired	Oct. 01, 1958	Oct. 01, 1958
Gross amount of real estate, Beginning Balance	98,508,199	95,832,358
Purchase of building improvements and equipment and construction in progress (expenditures advanced by Lessee, a related party, and recorded by Associates):	4,085,424	2,675,841
Gross amount of real estate, Assets sold/written off		(1,574,135)
Gross amount of real estate, Ending Balance	101,019,488	98,508,199
Accumulated depreciation, Beginning Balance	32,107,921	29,552,828
Depreciation	2,870,097	2,555,093
Accumulated depreciation, Assets sold/written off		(1,574,135)
Accumulated depreciation, Ending Balance	$ 33,403,883	$ 32,107,921
Building improvements and equipment [Member]
Gross amount at which carried at close of period
Life on which depreciation in latest income statements is computed	39 years	39 years
Equipment [Member]
Gross amount at which carried at close of period
Life on which depreciation in latest income statements is computed	7 years	7 years