Schedule III: Real estate and Accumulated depreciation (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 1,065,916
Initial cost of Land	21,593
Initial cost of Building, Leaseholds and Leasehold improvements	26,239
Costs capitalized subsequent to acquisition	863,960
Carrying amount of Land	44,971
Carring amount of Building, Leaseholds and Leasehold improvements	864,609
Construction in progress	2,212
Total carrying value of property	911,792
Accumulated depreciation and amortization	160,826
Differences Between Book and Tax Basis	184,806
Lexington Avenue Property [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	647,425
Initial cost of Land	14,432
Initial cost of Building, Leaseholds and Leasehold improvements	12,355
Costs capitalized subsequent to acquisition	424,822
Carrying amount of Land	27,497
Carring amount of Building, Leaseholds and Leasehold improvements	424,112
Construction in progress	0
Total carrying value of property	451,609
Accumulated depreciation and amortization	103,966
Date of construction	2003
Date acquired	1992
Lexington Avenue Property [Member] | Maximum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property, Plant and Equipment, Useful Life	39 years
Lexington Avenue Property [Member] | Minimum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property, Plant and Equipment, Useful Life	9 years
Rego Park 1 Shopping [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	78,246
Initial cost of Land	1,647
Initial cost of Building, Leaseholds and Leasehold improvements	8,953
Costs capitalized subsequent to acquisition	47,568
Carrying amount of Land	1,647
Carring amount of Building, Leaseholds and Leasehold improvements	56,400
Construction in progress	121
Total carrying value of property	58,168
Accumulated depreciation and amortization	24,534
Date of construction	1959
Date acquired	1992
Rego Park 1 Shopping [Member] | Maximum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property, Plant and Equipment, Useful Life	39 years
Rego Park 1 Shopping [Member] | Minimum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Rego Park 2 Property [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	272,245
Initial cost of Land	3,127
Initial cost of Building, Leaseholds and Leasehold improvements	1,467
Costs capitalized subsequent to acquisition	380,854
Carrying amount of Land	3,127
Carring amount of Building, Leaseholds and Leasehold improvements	382,041
Construction in progress	280
Total carrying value of property	385,448
Accumulated depreciation and amortization	31,612
Date of construction	2009
Date acquired	1992
Rego Park 2 Property [Member] | Maximum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Rego Park 2 Property [Member] | Minimum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Paramus Property [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	68,000
Initial cost of Land	1,441
Initial cost of Building, Leaseholds and Leasehold improvements	0
Costs capitalized subsequent to acquisition	10,313
Carrying amount of Land	11,754
Carring amount of Building, Leaseholds and Leasehold improvements	0
Construction in progress	0
Total carrying value of property	11,754
Accumulated depreciation and amortization	0
Date acquired	1992
Flushing Property [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial cost of Land	0
Initial cost of Building, Leaseholds and Leasehold improvements	1,660
Costs capitalized subsequent to acquisition	(107)
Carrying amount of Land	0
Carring amount of Building, Leaseholds and Leasehold improvements	1,553
Construction in progress	0
Total carrying value of property	1,553
Accumulated depreciation and amortization	672
Date of construction	1975
Date acquired	1992
Rego Park 3 Property [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial cost of Land	779
Initial cost of Building, Leaseholds and Leasehold improvements	0
Costs capitalized subsequent to acquisition	2,314
Carrying amount of Land	779
Carring amount of Building, Leaseholds and Leasehold improvements	503
Construction in progress	1,811
Total carrying value of property	3,093
Accumulated depreciation and amortization	42
Date acquired	1992
Rego Park 3 Property [Member] | Maximum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property, Plant and Equipment, Useful Life	15 years
Rego Park 3 Property [Member] | Minimum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Other Properties [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial cost of Land	167
Initial cost of Building, Leaseholds and Leasehold improvements	1,804
Costs capitalized subsequent to acquisition	(1,804)
Carrying amount of Land	167
Carring amount of Building, Leaseholds and Leasehold improvements	0
Construction in progress	0
Total carrying value of property	167
Accumulated depreciation and amortization	$ 0
Date acquired	1992