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Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands | Sep. 30, 2017 | Dec. 31, 2016
--- | --- | ---
ASSETS |  |  |
Real estate and development in process, net |  | $ 16,374,447 | $ 15,925,028
Liabilities and Members'/Partners' Equity [Abstract] |  |  |
Mortgage notes payable, net |  | 2,982,067 | 2,063,087
Other Liabilities |  | 419,215 | 450,821
Total liabilities and equity / capital |  | 19,308,518 | 18,851,643
Carrying value of the Company's investments in unconsolidated joint ventures |  | 611,800 | 775,198
Unconsolidated Joint Ventures [Member] |  |  |
ASSETS |  |  |
Real estate and development in process, net |  | 1,716,447 | 1,519,217
Other assets |  | 374,484 | 297,263
Total assets |  | 2,090,931 | 1,816,480
Liabilities and Members'/Partners' Equity [Abstract] |  |  |
Mortgage notes payable, net |  | 1,411,401 | 865,665
Other Liabilities |  | 86,971 | 67,167
Members'/Partners' equity |  | 592,559 | 883,648
Total liabilities and equity / capital |  | 2,090,931 | 1,816,480
Company's share of equity |  | 291,029 | 450,662
Basis differentials | [1] | 297,908 | 302,449
Carrying value of the Company's investments in unconsolidated joint ventures | [2],[3] | 588,937 | 753,111
Unconsolidated Joint Ventures [Member] |  |  |
Liabilities and Members'/Partners' Equity [Abstract] |  |  |
Basis differentials |  | 324,400 | 328,800
Carrying value of the Company's investments in unconsolidated joint ventures |  | $ (22,900) | $ (22,100)
[1] | This amount represents the aggregate difference between the Company’s historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials result from impairments of investments, acquisitions through joint ventures with no change in control and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. At September 30, 2017 and December 31, 2016, there was an aggregate basis differential of approximately $324.4 million and $328.8 million, respectively, between the carrying value of the Company’s investment in the joint venture that owns Colorado Center and the joint venture’s basis in the assets and liabilities, which differential (excluding land) shall be amortized over the remaining lives of the related assets and liabilities.
[2] | Investments with deficit balances aggregating approximately $22.9 million and $22.1 million at September 30, 2017 and December 31, 2016, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[3] | Investments with deficit balances aggregating approximately $22.9 million and $22.1 million at September 30, 2017 and December 31, 2016, respectively, have been reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.

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- Definition This amount represents the aggregate difference between the Company's historical cost basis and the basis reflected at the joint venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials occur from impairment of investments and upon the transfer of assets that were previously owned by the Company into a joint venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the joint venture level. + References No definition available. + Details
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- Definition Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(d)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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