Commitments And Contingencies (Details) (USD $)	2 Months Ended	7 Months Ended	9 Months Ended		5 Months Ended		3 Months Ended	12 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2014	Jul. 28, 2014	Sep. 30, 2014	Sep. 18, 2014	Jun. 09, 2014 767 Venture, LLC [Member]	Sep. 30, 2014 767 Venture, LLC [Member]	Sep. 30, 2014 Lehman [Member]	Dec. 31, 2009 Lehman [Member]	Jan. 10, 2014 Lehman [Member]	Sep. 30, 2014 Lehman [Member] Minimum [Member]	Sep. 30, 2014 Lehman [Member] Maximum [Member]	Sep. 30, 2014 John Hancock Tower [Member]	Sep. 30, 2014 601 Lexington Avenue [Member]
Commitments And Contingencies [Line Items]
Letter of credit and performance obligations	$ 19,100,000		$ 19,100,000
Maximum funding obligation						14,800,000
Guarantee Obligation Related To Tenant Re-Leasing Costs												28,800,000
Maturity Date												Jan. 06, 2017
Bankruptcy claim, amount filed by general creditor								45,300,000
Bankruptcy claim amount allowed by court to creditor							37,500,000		45,200,000
Bankruptcy Claims, Amount of Claims Settled				7,700,000
Bankruptcy claim, price on the private market										0.25	0.26
Bankruptcy claim, denominator used to evaluate claim price amount							1.00
Property insurance program per occurrence limits	1,000,000,000		1,000,000,000			1,625,000,000
Coverage For Acts Of Terrorism Under TRIA Covered in Excess of Amount Covered by IXP													250,000,000
Coverage for acts of Terrorism certified under TRIA in excess of amount provided by NYXP, LLC, as a direct insurer					1,375,000,000
Coverage for acts of terrorism certified under TRIA					250,000,000
Per occurrence limit for NBCR Coverage			1,000,000,000
Value of program trigger	100,000,000		100,000,000
Coinsurance of program trigger			15.00%
Deductible in insurance as a percentage of the value of the affected property, San Francisco			5.00%
Per occurrence limit of the earthquake insurance which covers San Francisco region			120,000,000
Annual aggregate limit of the earthquake insurance which covers San Francisco region			120,000,000
Amount of earthquake insurance provided by IXP, LLC as direct insurer San Francisco			20,000,000
Earthquake Coverage Included In Builders Risk Policy For 535 Mission			15,000,000
Earthquake Coverage Included In Builders Risk Policy For Salesforce Tower	60,000,000	15,000,000
Operating partnership guarantee to cover liabilities of IXP	$ 20,000,000		$ 20,000,000