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Investments in Unconsolidated Joint Ventures (Balance Sheets of the Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands | Jun. 30, 2020 | Dec. 31, 2019
--- | --- | ---
ASSETS |  |  |
Real estate and development in process, net |  | $ 17,668,420 | $ 17,622,212
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |
Mortgage and notes payable, net |  | 2,915,852 | 2,922,408
Other Liabilities |  | 373,281 | 387,994
Total liabilities and equity / capital |  | 23,000,777 | 21,284,905
Carying value of the Company's investment in unconsolidated joint ventures |  | 1,339,724 | 955,647
Right-of-use assets - finance leases |  | 237,394 | 237,394
Right of use assets - operating leases |  | 147,512 | 148,640
Lease liabilities - finance leases |  | 230,146 | 224,042
Lease liabilities - operating leases |  | 200,979 | 200,180
Unconsolidated Joint Ventures [Member] |  |  |
ASSETS |  |  |
Real estate and development in process, net | [1] | 4,527,828 | 3,904,400
Other assets |  | 535,870 | 502,706
Total assets |  | 5,063,698 | 4,407,106
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |
Mortgage and notes payable, net |  | 2,465,039 | 2,218,853
Other Liabilities | [2] | 655,709 | 749,675
Members'/Partners' equity |  | 1,942,950 | 1,438,578
Total liabilities and equity / capital |  | 5,063,698 | 4,407,106
Company's share of equity |  | 911,682 | 591,905
Basis differentials | [3] | 398,896 | 341,318
Carying value of the Company's investment in unconsolidated joint ventures | [4] | 1,310,578 | 933,223
Right-of-use assets - finance leases |  | 248,900 | 383,900
Right of use assets - operating leases |  | 11,700 | 12,100
Lease liabilities - finance leases |  | 390,200 | 510,800
Lease liabilities - operating leases |  | 17,400 | 17,300
Colorado Center [Member] |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |
Basis differentials |  | 309,000 | 311,300
Unconsolidated Joint Ventures [Member] |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |
Other Liabilities |  | 29,100 | $ 22,400
Gateway Commons Complex [Member] |  |  |
LIABILITIES AND MEMBERS'/PARTNERS' EQUITY |  |  |
Basis differentials |  | 54,400 |
Carying value of the Company's investment in unconsolidated joint ventures | [5] | $ 345,142 |
[1] | At June 30, 2020 and December 31, 2019, this amount includes right of use assets - finance leases totaling approximately $248.9 million and $383.9 million, respectively, and right of use assets - operating leases totaling approximately $11.7 million and $12.1 million, respectively.
[2] | At June 30, 2020 and December 31, 2019, this amount includes lease liabilities - finance leases totaling approximately $390.2 million and $510.8 million, respectively, and lease liabilities - operating leases totaling approximately $17.4 million and $17.3 million, respectively.
[3] | 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 June 30, 2020 and December 31, 2019, there was an aggregate basis differential of approximately $309.0 million and $311.3 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. At June 30, 2020, there was an aggregate basis differential of approximately $54.4 million between the carrying value of the Company’s investment in the joint venture that owns Gateway Commons and the joint venture’s basis in the assets and liabilities. These basis differentials (excluding land) will be amortized over the remaining lives of the related assets and liabilities.
[4] | Investments with deficit balances aggregating approximately $29.1 million and $22.4 million at June 30, 2020 and December 31, 2019, respectively, are reflected within Other Liabilities in the Company’s Consolidated Balance Sheets.
[5] | Investments with deficit balances aggregating approximately $29.1 million and $22.4 million at June 30, 2020 and December 31, 2019, respectively, are included within Other Liabilities in the Company’s Consolidated Balance Sheets.

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