Schedule III - Real Estate and Accumulated Depreciation Schedule of Real Estate and Accumulated Depreciation (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 1,208,112
Initial Cost to the Company
Initial Cost to the Company, Land	185,657
Initial Cost to the Company, Building & Leasehold	577,219
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	886,547
Gross Amount at which Carried
Gross Amount, Land	187,566
Gross Amount, Buildings & Improvements	1,461,857
Gross Amount, Total	1,649,423	939,330	856,151	796,008
Gross Amount, Accumulated Depreciation	(295,351)	(257,091)	(224,019)	(205,542)
1333 Broadway, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	78,121
Initial Cost to the Company
Initial Cost to the Company, Land	91,435
Initial Cost to the Company, Building & Leasehold	120,190
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	81
Gross Amount at which Carried
Gross Amount, Land	91,435
Gross Amount, Buildings & Improvements	120,271
Gross Amount, Total	211,706
Gross Amount, Accumulated Depreciation	(927)
1350 Broadway, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	56,848
Initial Cost to the Company
Initial Cost to the Company, Land	0
Initial Cost to the Company, Building & Leasehold	102,518
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	1,345
Gross Amount at which Carried
Gross Amount, Land	0
Gross Amount, Buildings & Improvements	103,863
Gross Amount, Total	103,863
Gross Amount, Accumulated Depreciation	(925)
250 West 57th Street, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	57,873
Initial Cost to the Company
Initial Cost to the Company, Land	2,117
Initial Cost to the Company, Building & Leasehold	5,041
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	67,432
Gross Amount at which Carried
Gross Amount, Land	2,117
Gross Amount, Buildings & Improvements	72,473
Gross Amount, Total	74,590
Gross Amount, Accumulated Depreciation	(19,775)
501 Seventh Avenue, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	45,925
Initial Cost to the Company
Initial Cost to the Company, Land	1,100
Initial Cost to the Company, Building & Leasehold	2,600
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	75,390
Gross Amount at which Carried
Gross Amount, Land	1,100
Gross Amount, Buildings & Improvements	77,990
Gross Amount, Total	79,090
Gross Amount, Accumulated Depreciation	(27,227)
1359 Broadway, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	45,023
Initial Cost to the Company
Initial Cost to the Company, Land	1,233
Initial Cost to the Company, Building & Leasehold	1,809
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	43,532
Gross Amount at which Carried
Gross Amount, Land	1,233
Gross Amount, Buildings & Improvements	45,341
Gross Amount, Total	46,574
Gross Amount, Accumulated Depreciation	(15,523)
350 Fifth Avenue (Empire State Building), New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	325,000
Initial Cost to the Company
Initial Cost to the Company, Land	21,551
Initial Cost to the Company, Building & Leasehold	38,934
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	471,196
Gross Amount at which Carried
Gross Amount, Land	21,551
Gross Amount, Buildings & Improvements	510,130
Gross Amount, Total	531,681
Gross Amount, Accumulated Depreciation	(35,264)
One Grand Central Place, New York, NY [Member] | Office/Retail [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	92,989
Initial Cost to the Company
Initial Cost to the Company, Land	7,240
Initial Cost to the Company, Building & Leasehold	17,490
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	137,599
Gross Amount at which Carried
Gross Amount, Land	7,240
Gross Amount, Buildings & Improvements	155,089
Gross Amount, Total	162,329
Gross Amount, Accumulated Depreciation	(57,124)
First Stamford Place, Stamford, CT [Member] | Office Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	245,629
Initial Cost to the Company
Initial Cost to the Company, Land	22,952
Initial Cost to the Company, Building & Leasehold	122,739
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	36,964
Gross Amount at which Carried
Gross Amount, Land	24,861
Gross Amount, Buildings & Improvements	157,794
Gross Amount, Total	182,655
Gross Amount, Accumulated Depreciation	(52,803)
One Station Place, Stamford, CT (Metro Center) [Member] | Office Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	96,158
Initial Cost to the Company
Initial Cost to the Company, Land	5,313
Initial Cost to the Company, Building & Leasehold	28,602
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	9,860
Gross Amount at which Carried
Gross Amount, Land	5,313
Gross Amount, Buildings & Improvements	38,462
Gross Amount, Total	43,775
Gross Amount, Accumulated Depreciation	(23,660)
383 Main Avenue, Norwalk, CT [Member] | Office Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	30,403
Initial Cost to the Company
Initial Cost to the Company, Land	2,262
Initial Cost to the Company, Building & Leasehold	12,820
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	9,320
Gross Amount at which Carried
Gross Amount, Land	2,262
Gross Amount, Buildings & Improvements	22,140
Gross Amount, Total	24,402
Gross Amount, Accumulated Depreciation	(8,573)
500 Mamaroneck Avenue, Harrison, NY [Member] | Office Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	32,620
Initial Cost to the Company
Initial Cost to the Company, Land	4,571
Initial Cost to the Company, Building & Leasehold	25,915
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	15,385
Gross Amount at which Carried
Gross Amount, Land	4,571
Gross Amount, Buildings & Improvements	41,300
Gross Amount, Total	45,871
Gross Amount, Accumulated Depreciation	(15,344)
10 Bank Street, White Plains, NY [Member] | Office Building [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	33,444
Initial Cost to the Company
Initial Cost to the Company, Land	5,612
Initial Cost to the Company, Building & Leasehold	31,803
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	8,681
Gross Amount at which Carried
Gross Amount, Land	5,612
Gross Amount, Buildings & Improvements	40,484
Gross Amount, Total	46,096
Gross Amount, Accumulated Depreciation	(14,448)
10 Union Square, New York, NY [Member] | Retail Site [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	20,972
Initial Cost to the Company
Initial Cost to the Company, Land	5,003
Initial Cost to the Company, Building & Leasehold	12,866
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	1,548
Gross Amount at which Carried
Gross Amount, Land	5,003
Gross Amount, Buildings & Improvements	14,414
Gross Amount, Total	19,417
Gross Amount, Accumulated Depreciation	(5,798)
1542 Third Avenue, New York, NY [Member] | Retail Site [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	19,011
Initial Cost to the Company
Initial Cost to the Company, Land	2,239
Initial Cost to the Company, Building & Leasehold	15,266
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	102
Gross Amount at which Carried
Gross Amount, Land	2,239
Gross Amount, Buildings & Improvements	15,368
Gross Amount, Total	17,607
Gross Amount, Accumulated Depreciation	(5,641)
1010 Third Avenue, New York, NY and 77 West 55th Street, New York, NY [Member] | Retail Site [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	28,096
Initial Cost to the Company
Initial Cost to the Company, Land	4,462
Initial Cost to the Company, Building & Leasehold	15,817
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	778
Gross Amount at which Carried
Gross Amount, Land	4,462
Gross Amount, Buildings & Improvements	16,595
Gross Amount, Total	21,057
Gross Amount, Accumulated Depreciation	(6,453)
69-97 Main Street, Westport, CT [Member] | Retail Site [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Initial Cost to the Company, Land	2,782
Initial Cost to the Company, Building & Leasehold	15,766
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	918
Gross Amount at which Carried
Gross Amount, Land	2,782
Gross Amount, Buildings & Improvements	16,684
Gross Amount, Total	19,466
Gross Amount, Accumulated Depreciation	(4,543)
103-107 Main Street, Westport, CT [Member] | Retail Site [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Initial Cost to the Company, Land	1,243
Initial Cost to the Company, Building & Leasehold	7,043
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	(41)
Gross Amount at which Carried
Gross Amount, Land	1,243
Gross Amount, Buildings & Improvements	7,002
Gross Amount, Total	8,245
Gross Amount, Accumulated Depreciation	(1,323)
Property for development at the Transportation Hub, Stamford, CT [Member] | Land [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Initial Cost to the Company, Land	4,542
Initial Cost to the Company, Building & Leasehold	0
Cost Capitalized Subsequent to Acquisition
Costs Capitalized Subsequent to Acquisition, Improvements	6,457
Gross Amount at which Carried
Gross Amount, Land	4,542
Gross Amount, Buildings & Improvements	6,457
Gross Amount, Total	10,999
Gross Amount, Accumulated Depreciation	$ 0