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Real Estate Joint Ventures (Details) $ in Thousands |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jul. 21, 2016 USD ($) | Jan. 31, 2016 USD ($) | Dec. 31, 2017 USD ($) ft² | Dec. 31, 2016 USD ($) Property | Dec. 31, 2015 USD ($)
Investments in consolidated real estate joint ventures |  |  |  |  |
Increase in property and redeemable noncontrolling interests in connection with property contribution by redeemable noncontrolling interests in a joint venture |  |  | $ 0 | $ 22,600 | $ 0
Distributions paid to redeemable noncontrolling interests |  |  | 8,215 | 15,206 | $ 2,993
Non-real estate equity method investments |  |  | 2,412 | $ 2,355 |
Consolidated real estate joint ventures [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Total Assets |  |  | 303,983 |  |
Encumbered Assets |  |  | 120,953 |  |
Total Liabilities |  |  | 116,830 |  |
Notes receivable from City of Huntsville [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Amount of advanced |  |  | 37,800 |  |
Single-tenant data centers [Member] | Operating office properties [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Increase in property and redeemable noncontrolling interests in connection with property contribution by redeemable noncontrolling interests in a joint venture | $ 147,600 |  |  |  |
Ownership percentage sold (percent) | 50.00% |  |  |  |
Ownership percentage | 50.00% |  |  |  |
Data Center Shells [Member] | Operating properties, net [Member] | Single-tenant data centers [Member] | Operating office properties [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Number of properties contributed | Property |  |  |  | 6 |
LW Redstone Company, LLC [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Partner's capital account upon formation |  |  | $ 9,000 |  |
Percentage of residual distributable cash flows in excess of unpaid cumulative preferred returns and return of invested capital entitled to the company |  |  | 85.00% |  |
Percentage of residual distributable cash flows in excess of unpaid cumulative preferred returns and return of invested capital entitled to the entity's partners |  |  | 15.00% |  |
Number of years following construction commencement threshold achievement before partner's interest can be purchased at fair value |  |  | 5 years |  |
Construction commencement threshold (in square feet) | ft² |  |  | 4,400,000.0 |  |
Construction commencement completed (in sqft) | ft² |  |  | 674,000 |  |
LW Redstone Company, LLC [Member] | Maximum [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Infrastructure costs anticipated to be funded by entity for reimbursement by the City of Huntsville (in dollars) |  |  | $ 76,000 |  |
Percentage of residual distributable cash flows in excess of unpaid cumulative preferred returns and return of invested capital entitled to the company |  |  | 85.00% |  |
Stevens Investors, LLC [Member] | Minimum [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Percentage of residual distributable cash flows in excess of unpaid cumulative preferred returns and return of invested capital entitled to the company |  |  | 60.00% |  |
M Square Associates, LLC [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Percentage of residual amounts distributed to each member |  |  | 50.00% |  |
GI-COPT [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Non-real estate equity method investments |  |  | $ 25,100 | $ 25,500 |
Difference between cost basis and share of underlying equity |  |  | $ 16,700 | 18,100 |
LW Redstone Company, LLC [Member] | Primary Beneficiary [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Ownership (as a percent) |  |  | 85.00% |  |
Total Assets |  |  | $ 158,891 |  |
Encumbered Assets |  |  | 75,569 |  |
Total Liabilities |  |  | $ 51,180 |  |
M Square Associates, LLC [Member] | Primary Beneficiary [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Ownership (as a percent) |  |  | 50.00% |  |
Total Assets |  |  | $ 73,116 |  |
Encumbered Assets |  |  | 45,384 |  |
Total Liabilities |  |  | $ 45,745 |  |
Stevens Investors, LLC [Member] | Primary Beneficiary [Member] |  |  |  |  |
Investments in consolidated real estate joint ventures |  |  |  |  |
Ownership (as a percent) |  |  | 95.00% |  |
Total Assets |  |  | $ 71,976 |  |
Encumbered Assets |  |  | 0 |  |
Total Liabilities |  |  | 19,905 |  |
Increase in property and redeemable noncontrolling interests in connection with property contribution by redeemable noncontrolling interests in a joint venture |  | $ 22,600 |  |  |
Distributions paid to redeemable noncontrolling interests |  |  | $ 6,700 | $ 13,400 |

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