Deferred Costs, Acquired Lease Intangibles and Goodwill Narrative (Details) (USD $)	3 Months Ended	12 Months Ended												12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Oct. 06, 2013 Empire State Building Observatory Operations [Member]	Oct. 06, 2013 Empire State Building, L.L.C. [Member]	Oct. 06, 2013 501 Seventh Avenue Associates [Member]	Dec. 31, 2013 Other Fees and Disbursements from Non-Controlled Affiliates [Member] Unconsolidated Properties [Member]	Dec. 31, 2012 Other Fees and Disbursements from Non-Controlled Affiliates [Member] Unconsolidated Properties [Member]	Dec. 31, 2011 Other Fees and Disbursements from Non-Controlled Affiliates [Member] Unconsolidated Properties [Member]	Dec. 31, 2013 Offering Costs for Work Done by Employees of Supervisor on Behalf of Option Properties [Member] Consolidated Properties [Member]	Dec. 31, 2012 Offering Costs for Work Done by Employees of Supervisor on Behalf of Option Properties [Member] Consolidated Properties [Member]	Dec. 31, 2011 Offering Costs for Work Done by Employees of Supervisor on Behalf of Option Properties [Member] Consolidated Properties [Member]	Dec. 31, 2013 Lease Agreements [Member]	Dec. 31, 2012 Lease Agreements [Member]	Dec. 31, 2011 Lease Agreements [Member]	Dec. 31, 2013 Leases and Deferred Leasing Costs [Member]	Dec. 31, 2013 Acquired above-market leases [Member]	Dec. 31, 2013 Below Market Lease [Member]
Deferred Costs [Line Items]
Amortization of deferred leasing costs		$ 10,600,000	$ 7,400,000	$ 6,400,000
Amortization of deferred finance costs and debt premiums	152,000	12,700,000	4,900,000	3,200,000
Offering costs	0	0	27,789,000					1,100,000	1,300,000	1,200,000	400,000	600,000	300,000
Amortization expense related to acquired lease intangibles														5,300,000	0	0
Amortization of acquired above and below-market leases, net	(1,911,000)	1,900,000	0	0
Weighted average useful life																	5 years 7 months 6 days	4 years 8 months 12 days	5 years 2 months 12 days
Goodwill	$ 491,479,000	$ 491,479,000			$ 227,500,000	$ 250,800,000	$ 13,200,000