Accounting Policies (Policies)	9 Months Ended
Accounting Policies (Policies)	Sep. 30, 2014
Accounting Policies [Abstract]
Change in Year-End	Change in Year-End The Company changed its year-end to December 31 from January 31, effective December 31, 2013. As a result, the financial results for the three and nine months ended September 30, 2013 are presented to allow for comparison between periods. The Company believes the change was useful to its financial statement users to allow for increased comparability of its performance to its peers.
Basis of Presentation	Basis of Presentation The interim consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and should be read in conjunction with the consolidated financial statements and related notes included in the Company’s annual report on Form 10-KT for the 11 months ended December 31, 2013, as amended on Form 10-KT/A on March 26, 2014. The results of interim periods are not necessarily indicative of results for the full year or any subsequent period. In management’s opinion, all adjustments (consisting solely of normal recurring matters) necessary for a fair statement of financial position, results of operations and cash flows at the dates and for the periods presented have been included.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires the Company to make estimates and assumptions in certain circumstances that affect amounts reported in the accompanying consolidated financial statements and related notes. Some of the critical estimates include, but are not limited to, determination of the primary beneficiary of variable interest entities (“VIEs”), estimates of useful lives for long-lived assets, reserves for collection on accounts and notes receivable and other investments, the fair value estimate of redeemable noncontrolling interest, impairment of real estate and other-than-temporary impairments on equity method investments. As a result of the nature of estimates, actual results could differ. In April 2013, management approved a plan to demolish Ten MetroTech Center, an office building in Brooklyn, New York, to clear the land for redevelopment or sale. Accordingly, the original useful life, estimated to expire in 2042, was adjusted to expire at the demolition date in October 2013, which resulted in $25,421,000 and $44,397,000 of accelerated depreciation expense recognized in the Consolidated Statements of Operations during the three and nine months ended September 30, 2013.
Reclassifications	Reclassifications During the nine months ended September 30, 2014, the Company established several new financial statement line items within the Revenue and Expense sections of the Consolidated Statement of Operations to provide the financial statement user additional details of the components of total revenues and total expenses. Accordingly, comparable amounts for the three and nine months ended September 30, 2013 have been reclassified. The new financial statement lines discussed above and a brief description of their components not previously disclosed include the following: Rental - Tenant rental revenues and overage rents from operating properties, lease termination income and the adjustment to recognize minimum rents using the straight-line method. Tenant recoveries - Recoveries from commercial tenants for common area maintenance, real estate taxes, insurance and other commercial property operating expenses. Service and management fees - Management, leasing, finance, development and other service fee revenue. Parking and other - Revenues derived from monthly and transient tenant parking and other revenue. Land sales - Sales of land to residential, commercial and industrial customers, primarily at the Company’s Stapleton project, and sales of commercial and residential outlots adjacent to the Company’s operating property portfolio. Property operating and management - Expenses incurred at the operating property level and general business unit expenses including non-capitalizable development costs and management and service company expenses. Ground rent - Expenses related to ground leases, including participation payments under the ground lease. Participation payments are triggered by defined events within the respective lease agreements and may include refinancings, sales or other capital transactions. Also includes the adjustment to recognize ground rent expenses using the straight-line method. Cost of land sales - Cost of land associated with land sales. Corporate general and administrative - Expenses related to the Company’s Corporate segment. In addition, The Nets operating segment information as of December 31, 2013 and for the three and nine months ended September 30, 2013 has been reclassified and aggregated with the Corporate Activities operating segment disclosures to conform to the current year presentation. Certain other prior year amounts in the accompanying consolidated financial statements have been reclassified to conform to the current year’s presentation.
Variable Interest Entities	Variable Interest Entities As of September 30, 2014, the Company determined it was the primary beneficiary of 23 VIEs representing 19 properties, which are consolidated. The creditors of the consolidated VIEs do not have recourse to the Company’s general credit. As of September 30, 2014, the Company owns variable interests in 62 VIEs for which it is not the primary beneficiary, which are accounted for as equity method investments. The maximum exposure to loss as a result of the ownership of these unconsolidated VIEs is limited to the Company’s applicable investment balances, which approximates $258,000,000 at September 30, 2014.
New Accounting Guidance	New Accounting Guidance The following accounting pronouncements were adopted during the nine months ended September 30, 2014: In July 2013, the Financial Accounting Standards Board (“FASB”) issued an amendment to the accounting guidance on the presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or tax credit carryforward exists. This guidance, which clarifies whether the unrecognized tax benefit should be recorded as a liability or reduction of the related deferred tax asset, is effective for fiscal years and interim reporting periods within those years, beginning after December 15, 2013. The amendments should be applied prospectively to all unrecognized tax benefits that exist at the effective date. Retrospective application is permitted. The adoption of this guidance on January 1, 2014 did not have a material impact on the Company’s consolidated financial statements. In April 2014, the FASB issued an amendment to the accounting guidance for reporting discontinued operations and disclosures of disposals of components of an entity. This guidance changes the requirements for reporting discontinued operations and the criteria for determining which disposals can be presented as discontinued operations. This guidance is effective for annual reporting periods beginning on or after December 15, 2014 and interim reporting periods within that annual period. Early adoption is permitted. This guidance was early adopted effective April 1, 2014. The adoption of this guidance is expected to substantially reduce the number of property disposals that qualify for discontinued operations as compared to historical results. The following new accounting pronouncements will be adopted on their respective effective dates: In August 2014, the FASB issued an amendment to the accounting guidance on disclosure of uncertainties about an entity’s ability to continue as a going concern. This guidance requires management to assess the Company’s ability to continue as a going concern and to provide disclosures under certain circumstances. This guidance is effective for annual reporting periods ending after December 15, 2016 and interim reporting periods thereafter. Early adoption is permitted. The Company does not expect the adoption of this guidance to have a material impact on the Company’s consolidated financial statements. In May 2014, the FASB issued an amendment to the accounting guidance for revenue from contracts with customers. The core principle of this guidance is an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The guidance defines steps an entity should apply to achieve the core principle. This guidance is effective for annual reporting periods beginning after December 15, 2016 and interim reporting periods within that annual period and allows for both retrospective and modified retrospective methods of adoption. Early adoption is not permitted. The Company is currently in the process of determining the method of adoption and evaluating the impact of adopting this guidance on the Company’s consolidated financial statements.
Fair Value of Other Financial Instruments	Fair Value of Other Financial Instruments The carrying amount of notes and accounts receivable, excluding the Stapleton advances, and accounts payable, accrued expenses and other liabilities approximates fair value based upon the short-term nature of the instruments. The carrying amount of the Stapleton advances approximates fair value since the interest rates on these advances approximates current market rates. The Company estimates the fair value of its debt instruments by discounting future cash payments at interest rates that the Company believes approximate the current market. Estimated fair value is based upon market prices of public debt, available industry financing data, current treasury rates, recent financing transactions and loan to value ratios. The fair value of the Company’s debt instruments is classified as Level 3 in the fair value hierarchy.

Disclosure of accounting policy for consolidation to describe the significant judgments and assumptions made in determining whether a variable interest held by the entity requires the variable interest entity to be consolidated and (or) disclose information about its involvement with the variable interest entity; the methodology used by the entity for determining whether or not it is the primary beneficiary of the variable interest entity; and the significant factors considered and judgments made in determining that the power to direct the activities that significantly impact the economic performance of the variable interest entity are shared (as defined).

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- Definition

Disclosure of accounting policy for determining an entity's fiscal year or other fiscal period. This disclosure may include identification of the fiscal period end-date, the length of the fiscal period, any reporting period lag between the entity and its subsidiaries, or equity investees. If a reporting lag exists, the closing date of the entity having a different period end is generally noted, along with an explanation of the necessity for using different closing dates. Any intervening events that materially affect the entity's financial position or results of operations are generally also disclosed.

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