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Noncontrolling Interests (Property Partnerships) (Narrative) (Details) - USD ($) $ in Thousands |  |  | 3 Months Ended |
--- | --- | --- | --- | ---
Apr. 01, 2019 | May 12, 2016 | Mar. 31, 2019 | Mar. 31, 2018 | Dec. 31, 2018
Noncontrolling Interest [Line Items] |  |  |  |  |
Noncontrolling Interest in Limited Partnerships |  |  | $ 1,710,608 |  | $ 1,711,445
Payments to Noncontrolling Interests |  |  | 24,128 | $ 30,690 |
Salesforce Tower [Member] | Consolidated Properties [Member] |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |
Portion of project costs covered by a construction loan |  | 50.00% |  |  |
Portion of costs funded (in percentage) |  | 50.00% |  |  |
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners |  | 5.00% |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 3.00% |  |  |
Salesforce Tower [Member] | Parent Company [Member] | Consolidated Properties [Member] |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |
Costs funded (in percentage) |  | 2.50% |  |  |
Preferred equity funded |  |  | $ 22,600 |  |
Salesforce Tower [Member] |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners | 5.00% |  |  |  |
Payments to Noncontrolling Interests | $ 210,900 |  |  |  |
Repayment of Preferred Equity | $ 24,100 |  |  |  |

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