Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Principles of Consolidation
Commercial real estate properties	$ 12,163,976us-gaap_RealEstateInvestmentPropertyNet	$ 10,687,540us-gaap_RealEstateInvestmentPropertyNet
Mortgages and other loans payable	5,586,709us-gaap_SecuredDebt	4,860,578us-gaap_SecuredDebt
Assets held for sale	462,430	0
Liabilities related to assets held for sale	266,873us-gaap_LiabilitiesOfAssetsHeldForSale	0us-gaap_LiabilitiesOfAssetsHeldForSale
Consolidated VIEs
Principles of Consolidation
Commercial real estate properties	198,400	605,900
Mortgages and other loans payable	106,500	370,900
Consolidated VIEs \| Commercial properties
Principles of Consolidation
Assets held for sale	445,000
Liabilities related to assets held for sale	$ 253,900

Represents the sum of the carrying value of all the Assets Held-for-Sale at the balance sheet date.

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Liability (such as a mortgage) related to a disposal group that is held for sale and anticipated to be sold in less than one year. The liability is expected to be discharged as part of the plan of sale for the asset.

+ References

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Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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