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Investment in Unconsolidated Real Estate Ventures (Textual) (Details) |  |  |  |  |  |  |  |  |  | 3 Months Ended | 9 Months Ended |  |  |  |  |  |  |
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Oct. 24, 2016 USD ($) | Sep. 22, 2016 USD ($) | Aug. 31, 2016 USD ($) | Aug. 19, 2016 USD ($) | Jun. 30, 2016 USD ($) ft² | Jun. 10, 2016 USD ($) | Mar. 02, 2016 USD ($) | Feb. 04, 2016 USD ($) ft² property | Jan. 29, 2016 USD ($) | Sep. 30, 2016 USD ($) | Jun. 30, 2016 USD ($) ft² | Sep. 30, 2015 USD ($) | Sep. 30, 2016 USD ($) property | Sep. 30, 2015 USD ($) | Sep. 30, 2016 | Sep. 30, 2016 property | Sep. 30, 2016 ft² | Sep. 30, 2016 Real_Estate_Investment | Sep. 30, 2016 a | Sep. 30, 2016 Apartment_unit | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) a Storey Bed | Sep. 30, 2014 a Storey Bed | Jan. 25, 2013 USD ($) a | Jul. 10, 2012 USD ($) ft² property | Dec. 20, 2011 property
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Management fees |  |  |  |  |  |  |  |  |  |  | $ 6,248,000 |  | $ 4,274,000 | $ 17,691,000 | $ 12,805,000 |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable |  |  |  |  |  |  |  |  |  |  | 9,925,000 |  |  | 9,925,000 |  |  |  |  |  |  |  | $ 17,126,000 |  |  |  |  |
Deconsolidated mortgage loan |  |  |  |  |  |  |  |  |  |  |  |  |  | 20,582,000 | 0 |  |  |  |  |  |  |  |  |  |  |  |
Deconsolidated financing liability |  |  |  |  |  |  |  |  |  |  |  |  |  | 12,384,000 | 0 |  |  |  |  |  |  |  |  |  |  |  |
Investment in Real Estate Ventures, equity method |  |  |  |  |  |  |  |  |  |  | 282,162,000 |  |  | 282,162,000 |  |  |  |  |  |  |  | 241,004,000 |  |  |  |  |
Capital funded to venture for mortgage debt |  |  |  |  |  |  |  |  |  |  |  |  |  | 27,174,000 | 62,868,000 |  |  |  |  |  |  |  |  |  |  |  |
Repayment of mortgage debt |  |  |  |  |  |  |  |  |  |  |  |  |  | 302,514,000 | 10,598,000 |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties | property |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 117 |  |  |  |  |  |  |  |  |  |
Proceeds from sale of real estate venture |  |  |  |  |  |  |  |  |  |  |  |  |  | 20,551,000 | 0 |  |  |  |  |  |  |  |  |  |  |  |
Net gain on Real Estate Venture transactions |  |  |  |  |  |  |  |  |  |  | 10,472,000 |  | 0 | 19,529,000 | 0 |  |  |  |  |  |  |  |  |  |  |  |
Advance received for refinancing |  |  |  |  |  |  |  |  |  |  |  |  |  | 195,000,000 | 0 |  |  |  |  |  |  |  |  |  |  |  |
Cash distribution from unconsolidated real estate ventures |  |  |  |  |  |  |  |  |  |  |  |  |  | 12,565,000 | 7,401,000 |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from the sale of properties |  |  |  |  |  |  |  |  |  |  |  |  |  | 758,931,000 | 152,243,000 |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  |  |  |  |  | (104,000) |  | 6,083,000 | 114,625,000 | 16,673,000 |  |  |  |  |  |  |  |  |  |  |  |
TB-BDN Plymouth Apartments [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Construction Loan |  |  |  |  |  |  |  |  |  |  | 56,000,000 |  |  | 56,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Guarantor obligations, current carrying value |  |  |  |  |  |  |  |  |  |  | 3,200,000 |  |  | 3,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |
1919 Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Guarantor obligations, current carrying value |  |  |  |  |  |  |  |  |  |  | 88,900,000 |  |  | 88,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Office Properties [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,082,963 |  |  |  |  |  |  |  |  |
Number of Properties | property |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 99 |  |  |  |  |  |  |  |  |  |
Sales Price |  |  |  |  |  |  |  |  |  |  | 807,200,000 |  |  | $ 807,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  |  |  |  |  |  | 63 |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from the sale of properties |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 757,785,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale | [1] |  |  |  |  |  |  |  |  |  |  |  |  | 114,601,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Office Properties [Member] | 3141 Fairview Park Drive [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 587,317 |  |  |  |  |  |  |  |  |
Real Estate Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Management fees |  |  |  |  |  |  |  |  |  |  | 6,200,000 |  | $ 4,300,000 | 17,700,000 | $ 12,800,000 |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable |  |  |  |  |  |  |  |  |  |  | 1,100,000 |  |  | 1,100,000 |  |  |  |  |  |  |  | 1,700,000 |  |  |  |  |
Unconsolidated Real Estate Ventures [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 14 |  |  |  |  |  |  |  |
Equity Method Investments including net liabilities |  |  |  |  |  |  |  |  |  |  | 282,200,000 |  |  | 282,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Investment in Real Estate Ventures, equity method | [2],[3] |  |  |  |  |  |  |  |  |  | 282,162,000 |  |  | 282,162,000 |  |  |  |  |  |  |  | 241,004,000 |  |  |  |  |
Unconsolidated Real Estate Ventures [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20.00% |  |  |  |  |  |  |  |  |  |  |
Unconsolidated Real Estate Ventures [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 70.00% |  |  |  |  |  |  |  |  |  |  |
Unconsolidated Real Estate Ventures [Member] | Seven Real Estate Ventures [Member] | Office Properties [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7 |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8,000,000 |  |  |  |  |  |  |  |  |
Unconsolidated Real Estate Ventures [Member] | Two Real Estate Ventures [Member] | Undeveloped Land [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |
Acreage of land | a |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.3 |  |  |  |  |  |  |
Unconsolidated Real Estate Ventures [Member] | Two Other Real Estate Ventures [Member] | Under Active Development Land [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |
Acreage of land | a |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.4 |  |  |  |  |  |  |
Unconsolidated Real Estate Ventures [Member] | Two Other Real Estate Ventures [Member] | Residential Tower One [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |  |  |  |  |
Number of Property units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 345 |  |  |  | 345 |  |  |  |  |  |
Unconsolidated Real Estate Ventures [Member] | Two Other Real Estate Ventures [Member] | Residential Tower Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |  |  |  |  |
Number of Property units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 321 |  |  |  | 321 |  |  |  |  |  |
Unconsolidated Real Estate Ventures [Member] | One Real Estate Venture [Member] | Apartment Complex [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Unconsolidated Investments in Real Estate Ventures | Real_Estate_Investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |  |  |  |  |
Number of Property units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 398 |  |  |  | 398 |  |  |  |  |  |
Brandywine - AI Venture LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00%
Provision for impairment of investment in real estate ventures |  |  |  |  |  |  |  |  |  |  |  |  |  | 10,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Brandywine - AI Venture LLC [Member] | Current Creek Investments, LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00%
Brandywine - AI Venture LLC [Member] | 3141 Fairview Park Drive [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deconsolidated net assets |  |  |  | $ 45,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deconsolidated mortgage loan |  |  |  | 20,582,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deconsolidated financing liability |  |  |  | 12,384,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment in Real Estate Ventures, equity method |  |  |  | $ 12,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Recognizing gain or loss on sale |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capital funded to venture for mortgage debt |  |  |  |  |  |  |  |  |  |  |  |  |  | 10,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Brandywine - AI Venture LLC [Member] | 3141 Fairview Park Drive [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayment of mortgage debt |  | $ 20,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Brandywine - AI Venture LLC [Member] | Station Square [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 497,896 |
Equity method investment percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% |
Provision for impairment of investment in real estate ventures |  |  |  |  |  |  |  |  |  |  |  |  |  | 10,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties | property |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |
Cost of equity method investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 120,600,000 |
Equity method investment other than temporary impairment charge |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Brandywine - AI Venture LLC [Member] | Remaining Properties in Real Estate Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment other than temporary impairment charge |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |  |  |  |
Brandywine - AI Venture LLC [Member] | Office Properties [Member] | 3141 Fairview Park Drive [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of office properties owned | property |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3
PJP V [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  | 25.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from sale of real estate venture |  |  | $ 3,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity in income (loss) of Real Estate Ventures |  |  | 200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net gain on Real Estate Venture transactions |  |  | $ 3,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PJP V [Member] | Office Properties [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 73,997 |  |  |  |  |  |  |  |  |
Invesco Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity in income (loss) of Real Estate Ventures |  |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net gain on Real Estate Venture transactions |  |  |  |  | 7,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proceeds, net of closing costs |  |  |  |  | $ 7,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
1000 Chesterbrook [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  | 50.00% |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from sale of real estate venture |  |  |  |  |  | $ 9,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net gain on Real Estate Venture transactions |  |  |  |  |  | 3,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sales Price |  |  |  |  |  | 32,100,000 |  |  |  |  |  | $ 32,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt assumed by buyer |  |  |  |  |  | $ 23,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Working capital contribution |  |  |  |  |  |  |  |  |  |  | 200,000 |  |  | $ 200,000 |  |  |  |  |  |  |  |  |  |  |  |  |
1000 Chesterbrook [Member] | One Real Estate Venture [Member] | Office Properties [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net Rentable Square Feet | ft² |  |  |  |  |  | 172,286 |  |  |  |  |  | 172,286 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
evo at Cira Centre South Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30.00% |  |
Investment in Real Estate Ventures, equity method |  |  |  |  |  |  |  | $ 28,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity Method Investment, Underlying Equity in Net Assets |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 |  | $ 8,500,000 |  |
Area of developed parcels of land (in acres) owned by a Real Estate Venture | a |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 1 | 1 |  |
Number of floors of a building | Storey |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 33 |  |  |
Student housing bed capacity | Bed |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 850 |  |  |
Percent of share of contribution made on real estate venture |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 100.00% |  | 0.00% |  |
Construction Loan |  |  |  |  |  |  | $ 97,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 97,800,000 |  | $ 0 |  |
Cash paid to acquire real estate ventures |  |  |  |  |  |  |  | $ 12,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage of interests acquired by the Company and HSRE |  |  |  |  |  |  |  | 30.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument maturity date |  |  |  |  |  |  | Jul. 25, 2016 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash distribution from unconsolidated real estate ventures |  |  |  |  |  |  | $ 6,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
evo at Cira Centre South Venture [Member] | Secured Debt [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument maturity date |  |  |  |  |  |  | Oct. 31, 2019 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term loans |  |  |  |  |  |  | $ 117,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, description of variable rate basis |  |  |  |  |  |  |  |  |  |  |  |  |  | LIBOR + 2.25 |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument optional extended maturity date |  |  |  |  |  |  | Jun. 30, 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Advance received for refinancing |  |  |  |  |  |  | $ 105,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional capacity under the term loan may be funded if certain criterion relating to the operating performance of the student housing tower are met |  |  |  |  |  |  | $ 12,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
evo at Cira Centre South Venture [Member] | Secured Debt [Member] | LIBOR [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, basis spread on variable rate |  |  |  |  |  |  | 2.25% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
evo at Cira Centre South Venture [Member] | Campus Crest Properties, LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30.00% |  |
evo at Cira Centre South Venture [Member] | HSRE, LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40.00% |  |
Cash paid to acquire real estate ventures |  |  |  |  |  |  |  | $ 6,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
evo at Cira Centre South Venture [Member] | Maximum [Member] | Secured Debt [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Effective interest rate |  |  |  |  |  |  | 5.25% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
MAP Venture [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  | 3,924,783 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sales Price |  |  |  |  |  |  |  |  | $ 398,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  | 58 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of fee interests in land sold |  |  |  |  |  |  |  |  | 100.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ground lease annual payments |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 11,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Ground lease annual rent expense increase percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.50% |  |  |  |  |  |  |  |  |  |  |
Reassessment period for change in ground lease annual payments |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |
Ground Lease Terms |  |  |  |  |  |  |  |  |  |  |  |  |  | Annual payments by the MAP Venture, as tenant under the Ground Leases, initially total $11.9 million and increase 2.5% annually through November 2025. |  |  |  |  |  |  |  |  |  |  |  |  |
Non-Recourse Debt |  |  |  |  |  |  |  |  | $ 180,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from the sale of properties |  |  |  |  |  |  |  |  | 354,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership percentage value |  |  |  |  |  |  |  |  | $ 25,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Coppell Associates [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from sale of real estate venture |  |  |  |  |  |  |  |  |  | $ 4,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  |  |  |  | 5,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Coppell Associates [Member] | Other Liabilities [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |
Investment in Real Estate Ventures, equity method |  |  |  |  |  |  |  |  |  | $ 1,100,000 | 0 |  |  | $ 0 |  |  |  |  |  |  |  | $ 1,100,000 |  |  |  |  |
PJP VII [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Guarantor obligations, current carrying value |  |  |  |  |  |  |  |  |  |  | $ 500,000 |  |  | $ 500,000 |  |  |  |  |  |  |  |  |  |  |  |  |
[1] | Gain/(Loss) on Sale is net of closing and other transaction related costs.
[2] | Does not include the negative investment balance in one real estate venture totaling $1.1 million as of December 31, 2015, which is included in other liabilities. There is no negative investment balance as of September 30, 2016 because the Company sold its entire remaining 50% interest in the applicable real estate venture (See “Coppell Associates” section below) during the three month period ended March 31, 2016.
[3] | This amount includes the effect of the basis difference between the Company's historical cost basis and the basis recorded at the Real Estate Venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials occur from the impairment of investments, purchases of third party interests in existing Real Estate Ventures and upon the transfer of assets that were previously owned by the Company into a Real Estate Venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the Real Estate Venture level.

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