Accounting Policies (Policies)	6 Months Ended
Accounting Policies (Policies)	Jul. 31, 2013
Accounting Policies [Abstract]
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-K for the year ended January 31, 2013, as amended on Form 10-K/A on April 30, 2013. 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 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 made by the Company 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, impairment of real estate and other-than-temporary impairments on its equity method investments. As a result of the nature of estimates made by the Company, 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 its redevelopment or sale. Accordingly, the estimated useful life of Ten MetroTech Center was adjusted to expire at the anticipated scheduled demolition date in September 2013, which resulted in $25,258,000 and $27,283,000 of accelerated depreciation expense recognized in the Consolidated Statements of Operations during the three and six months ended July 31, 2013.
Reclassifications	Reclassifications During the year ended January 31, 2013, the Company determined that Barclays Center (the "Arena"), a sports and entertainment arena located in Brooklyn, New York, met the criteria for a reportable operating segment. Therefore, the segment reporting disclosures related to Barclays Center as of and for the three and six months ended July 31, 2012 have been reclassified from the Commercial Group segment to the Arena segment (see Note P – Segment Information). 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 The Company’s VIEs consist of joint ventures that are engaged in the ownership, development and management of office buildings, regional malls, specialty retail centers, apartment communities, military housing and The Nets, a member of the National Basketball Association (“NBA”). As of July 31, 2013, the Company determined that it was the primary beneficiary of 30 VIEs representing 22 properties, which are consolidated. The creditors of the consolidated VIEs do not have recourse to the Company’s general credit. As of July 31, 2013, the Company held variable interests in 63 VIEs for which it is not the primary beneficiary, which are unconsolidated. 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 $64,000,000 at July 31, 2013.
Noncontrolling Interest	Noncontrolling Interest Interests held by partners in consolidated entities are reflected in noncontrolling interest, which represents the noncontrolling interests’ share of the underlying net assets of the Company’s consolidated subsidiaries. Noncontrolling interest that is not redeemable is reported in the equity section of the Consolidated Balance Sheets. Noncontrolling interests where the Company may be required to repurchase the noncontrolling interest at fair value under a put option or other contractual redemption requirement are reported in the mezzanine section of the Consolidated Balance Sheets between liabilities and equity, as redeemable noncontrolling interest. The Company adjusts the redeemable noncontrolling interest to redemption value (which approximates fair value) at each balance sheet date with changes recognized as an adjustment to additional paid-in capital (see Note F – Fair Value Measurements).
New Accounting Guidance	New Accounting Guidance The following accounting pronouncements were adopted during the six months ended July 31, 2013: In July 2013, the Financial Accounting Standards Board ("FASB") issued an amendment to the accounting guidance on the use of benchmark interest rates for hedge accounting. This guidance provides an entity the option to use the Fed Funds Effective Swap Rate, in addition to the rate on United States Treasuries and London Interbank Offered Rate ("LIBOR"), for hedge accounting purposes. The guidance also removes restrictions on using different benchmark rates for similar hedges. This guidance is effective prospectively for qualifying new or redesignated hedging relationships entered into on or after July 17, 2013. The adoption of this guidance on July 17, 2013 did not have a material impact on the Company's consolidated financial statements. In February 2013, the FASB issued an amendment to the accounting guidance for the reporting of amounts reclassified out of accumulated OCI. This guidance does not change the current requirements for reporting net income or other comprehensive income in financial statements. However, the amendments require an entity to provide information about the amounts reclassified out of accumulated OCI by component. In addition, an entity is required to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated OCI by the respective line items of net income but only if the amount reclassified is required under GAAP to be reclassified to net income in its entirety in the same reporting period. For other amounts that are not required under GAAP to be reclassified in their entirety to net income, an entity is required to cross-reference to other disclosures required under GAAP that provide additional detail about those amounts. This guidance is effective prospectively for reporting periods beginning after December 15, 2012. The required disclosures upon adoption of this guidance on February 1, 2013 are included in the Company’s consolidated financial statements. In July 2012, the FASB issued an amendment to the accounting guidance on testing indefinite-lived intangible assets for impairment. This guidance provides an entity the option to first assess qualitative factors to determine whether the existence of events and circumstances indicates that it is more likely than not that the indefinite-lived intangible asset is impaired. If an entity concludes that it is not more likely than not that the asset is impaired, then the entity is not required to take further action. If an entity concludes otherwise, it is required to determine the fair value of the indefinite-lived intangible asset and perform the quantitative test by comparing the fair value with the carrying amount. This guidance is effective for annual and interim impairment tests performed for fiscal years beginning after September 15, 2012. The adoption of this guidance on February 1, 2013 did not have a material impact on the Company’s consolidated financial statements. In December 2011, the FASB issued an amendment to the accounting guidance on derecognition of in substance real estate. This guidance specifies that when a parent company (reporting entity) ceases to have a controlling financial interest (as described in the accounting guidance on consolidation) in a subsidiary that is in substance real estate as a result of a default on the subsidiary’s nonrecourse debt, the reporting entity should apply the guidance on property, plant and equipment to determine whether it should derecognize the in substance real estate. Generally, a reporting entity would not satisfy the requirements to derecognize the in substance real estate before the legal transfer of the real estate to the lender and the extinguishment of the related nonrecourse indebtedness. This guidance is effective for fiscal years and interim reporting periods within those years, beginning on or after June 15, 2012. The adoption of this guidance on February 1, 2013 did not impact the Company’s consolidated financial statements or their comparability to previously issued financial statements as the guidance in this amendment is consistent with the Company's previous accounting policies. In December 2011, the FASB issued an amendment to the accounting guidance that requires entities to disclose both gross and net information on financial instruments and transactions eligible for offset on the balance sheets and financial instruments and transactions subject to an agreement similar to a master netting arrangement. In January 2013, the FASB issued guidance clarifying that the scope of disclosures about offsetting assets and liabilities should apply only to derivatives and hedging instruments. This guidance is effective for annual and interim reporting periods beginning on or after January 1, 2013. The adoption of this guidance on February 1, 2013 did not have a material impact 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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