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Real Estate Investments - Summary of Office Properties Sold (Parenthetical) (Details) |  | 3 Months Ended | 12 Months Ended |  |  |  |
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Feb. 04, 2016 property | Jun. 30, 2016 USD ($) | Mar. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) ft² Storey | Jun. 30, 2015 USD ($) | Mar. 31, 2015 USD ($) | Sep. 30, 2014 USD ($) | Dec. 31, 2016 USD ($) ft² property | Dec. 31, 2015 USD ($) ft² property Storey | Dec. 31, 2014 USD ($) ft² property Storey | Oct. 17, 2014 ft² | Jul. 31, 2014 ft² | Apr. 03, 2014 USD ($) ft² Storey | Oct. 16, 2013 USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Provision for impairment |  |  | $ 1,800,000 |  |  |  |  |  | $ 40,517,000 |  | $ 82,208,000 |  | $ 1,765,000 |  |  |  |  |
Impairment of properties held for use |  |  |  |  |  |  |  |  | 7,300,000 |  |  |  |  |  |  |  |  |
Gain (loss) on real estate venture transactions |  |  |  |  |  |  |  |  | 20,000,000 |  | 7,229,000 |  | (417,000) |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  |  |  | $ 116,983,000 |  | $ 20,496,000 |  | $ 4,901,000 |  |  |  |  |
Austin Joint Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 590,881 | 232,274 |  |
Brandywine Realty Trust [Member] | Austin Joint Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate gross sales price of a joint venture |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 330,000,000
Encino Trace [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |
Number of floors of a building | Storey |  |  |  |  | 4 |  |  |  |  |  | 4 |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  | 320,000 |  |  |  |  |  | 320,000 |  |  |  |  |  |  |
Encino Trace [Member] | Austin Joint Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Project expected cost |  |  |  |  |  |  |  |  |  |  | $ 91,300,000 |  |  |  |  |  |  |
Non-Recourse Debt |  |  |  |  | $ 30,000,000 |  |  |  |  |  | 30,000,000 |  |  |  |  |  |  |
Amount Of Participant Contribution |  |  |  |  | 1,800,000 |  |  |  |  |  | 1,800,000 |  |  |  |  |  |  |
Encino Trace [Member] | Brandywine Realty Trust [Member] | Austin Joint Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Development costs |  |  |  |  | 76,700,000 |  |  |  |  |  | 76,700,000 |  |  |  |  |  |  |
Proceeds from Equity Method Investment, Dividends or Distributions |  |  |  |  |  |  |  |  |  |  | 50,200,000 |  |  |  |  |  |  |
Capital contribution |  |  |  |  | 23,300,000 |  |  |  |  |  | 23,300,000 |  |  |  |  |  |  |
Gain (loss) on real estate venture transactions |  |  |  |  |  |  |  |  |  |  | 2,000,000 |  |  |  |  |  |  |
Additional borrowing fund to tenant improvements and leasing commissions |  |  |  |  | 29,700,000 |  |  |  |  |  | 29,700,000 |  |  |  |  |  |  |
Encino Trace [Member] | DRA Advisors LLC [Member] | Austin Joint Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Working capital contribution |  |  |  |  | 1,800,000 |  |  |  |  |  | 1,800,000 |  |  |  |  |  |  |
Encino Trace [Member] | DRA Advisors LLC [Member] | Brandywine Realty Trust [Member] | Austin Joint Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount Of Participant Contribution |  |  |  |  | $ 25,100,000 |  |  |  |  |  | $ 25,100,000 |  |  |  |  |  |  |
100, 101, 200, 300 and 301 Lindenwood Drive (the Valleybrooke Properties) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Provision for impairment on assets held for sale |  |  |  |  |  |  |  | $ 1,800,000 |  |  |  |  |  |  |  |  |  |
11305 Four Points Drive (Four Points Centre) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |
Number of floors of a building | Storey |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  | 3 |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  |  |  |  |  | 192,396 |  |  |  |  |
11305 Four Points Drive (Four Points Centre) [Member] | Austin Joint Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Non-Recourse Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 29,000,000 |
11305 Four Points Drive (Four Points Centre) [Member] | Brandywine Realty Trust [Member] | Austin Joint Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount Of Participant Contribution |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,900,000 |
Gain (loss) on real estate venture transactions |  |  |  |  |  |  |  |  |  |  |  |  | $ (200,000) |  |  |  |  |
Additional borrowing fund to tenant improvements and leasing commissions |  |  |  |  |  |  |  |  |  |  |  |  | $ 34,400,000 |  |  |  |  |
Aggregate gross sales price of a joint venture |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 41,500,000 |
Office Properties [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  | 66 |  | 27 |  | 8 |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  | 2,649,926 |  |  |  | 5,239,632 |  | 2,649,926 |  | 645,273 |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  |  |  | $ 116,983,000 | [1] | $ 22,002,000 | [2],[3] | $ 4,646,000 | [4] |  |  |  |
Deferred gain |  |  |  |  | $ 500,000 |  |  |  |  |  | $ 500,000 |  |  |  |  |  |  |
Office Properties [Member] | 196/198 Van Buren Street (Herndon Metro Plaza I&II) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Impairment of properties held for use |  |  |  | $ 7,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  | 197,225 |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale | [1],[5] |  |  |  |  |  |  |  | $ (752,000) |  |  |  |  |  |  |  |  |
Office Properties [Member] | Och Ziff Portfolio [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  | 58 |  |  |  |  |  |  | 58 | [6] |  |  |  |  |  |  |  |
Provision for impairment on assets held for sale |  |  |  |  | $ 45,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² | [6] |  |  |  |  |  |  |  | 3,924,783 |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale | [1],[6],[7] |  |  |  |  |  |  |  | $ (372,000) |  |  |  |  |  |  |  |  |
Office Properties [Member] | Encino Trace [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  | 320,000 |  |  |  |  |  | 320,000 |  |  |  |  |  |  |
Gain (Loss) on Sale | [2],[8] |  |  |  |  |  |  |  |  |  | $ 2,008,000 |  |  |  |  |  |  |
Office Properties [Member] | Carlsbad, CA [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Provision for impairment on assets held for sale |  |  |  |  | $ 6,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  |  |  |  |
Office Properties [Member] | 100 Gateway Centre Parkway [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |  |  |  |
Provision for impairment on assets held for sale |  |  |  |  |  | $ 800,000 |  |  |  |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  | 74,991 |  |  |  |  |  | 74,991 |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  | $ 0 |  |  |  |  | $ 0 | [2],[9] |  |  |  |  |  |
Office Properties [Member] | Lake Merritt Tower [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |  |  |  |
Provision for impairment on assets held for sale |  |  |  |  |  |  | $ 1,700,000 |  |  |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  | 204,336 |  |  |  |  |  | 204,336 |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  | $ 0 |  |  |  | $ 0 | [2],[10] |  |  |  |  |  |
Office Properties [Member] | 100, 101, 200, 300 and 301 Lindenwood Drive (the Valleybrooke Properties) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  |  |  |  |  | 5 |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  |  |  |  |  | 279,934 |  |  |  |  |
Gain (Loss) on Sale | [4],[11] |  |  |  |  |  |  |  |  |  |  |  | $ 203,000 |  |  |  |  |
Office Properties [Member] | 11305 Four Points Drive (Four Points Centre) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Properties Sold | property |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  |  |  |  |  | 192,396 |  |  |  |  |
Gain (Loss) on Sale | [4],[12] |  |  |  |  |  |  |  |  |  |  |  | $ (255,000) |  |  |  |  |
Office Properties [Member] | 11305 Four Points Drive (Four Points Centre) [Member] | Austin Joint Venture [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rentable Square Feet | ft² |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 192,396 |
[1] | Gain/(Loss) on Sale is net of closing and other transaction related costs.
[2] | Gain on Sale is net of closing and other transaction related costs.
[3] | Total gain on sale does not include a deferred gain of $0.5 million related to a prior sale.
[4] | Gain/(Loss) on sale is net of closing and other transaction related costs.
[5] | During the three-month period ended March 31, 2016, the Company recognized a provision for impairment totaling approximately $7.4 million on the properties. See “Held for Use Impairment” section below. The loss on sale primarily relates to additional closing costs recognized at closing.
[6] | Exhibit 99.2 to the Company’s Current Report on Form 8-K filed on February 10, 2016 contains a complete list of the 58 properties disposed of in the transactions with Och-Ziff Capital Management Group LLC. See Note 4, "Investment in Unconsolidated Real Estate Ventures," for further details of the transactions.
[7] | During the three-month period ended December 31, 2015, the Company recognized a provision for impairment totaling approximately $45.4 million. The loss on sale represents additional closing costs recognized at closing.
[8] | On December 31, 2015, the Company contributed two newly constructed four-story, Class A office buildings, commonly known as “Encino Trace,” containing an aggregate of approximately 320,000 square feet in Austin, Texas to one of its existing real estate ventures (the “Austin Venture”) that the Company formed in 2013 with G&I VII Austin Office LLC, an investment vehicle advised by DRA Advisors LLC (“DRA”). When these two properties were contributed to the Austin Venture the Company had incurred a total of $76.7 million of development costs, representing the contribution value. The project is expected to cost $91.3 million with remaining costs fully funded by the Austin Venture. In conjunction with the contribution: (i) the Austin Venture obtained a $30.0 million mortgage loan; (ii) DRA contributed $25.1 million in net cash to the capital of the Austin Venture, including a $1.8 million working capital contribution; and (iii) the Austin Venture distributed $50.2 million to the Company and credited the Company with a $23.3 million capital contribution to the Austin Venture. In addition to the contribution of the properties, the Company also made a $1.8 million cash contribution to the Austin Venture for working capital. The Company recognized a $2.0 million gain on the contribution. Under the Encino Trace loan agreement the Austin Venture has the option, subject to certain leasing and loan-to-value requirements, to borrow an additional $29.7 million to fund tenant improvements and leasing commissions.
[9] | The Company recorded an impairment loss of $0.8 million for 100 Gateway Centre Parkway during the second quarter of 2015. As such, there was no gain at disposition for this property.
[10] | The Company recorded an impairment loss of $1.7 million for Lake Merritt Tower at March 31, 2015. As such, there was no gain at disposition for this property. Sales proceeds were deposited in escrow under Section 1031 of the Internal Revenue Code and applied to purchase the Broadmoor Austin portfolio. Refer to Broadmoor Austin Associates acquisition summary, above, for further details.
[11] | During the third quarter of 2014, the Company recorded a $1.8 million impairment loss on these properties.
[12] | On April 3, 2014, the Company contributed two three-story, Class A office buildings, commonly known as “Four Points Centre,” containing an aggregate of approximately 192,396 net rentable square feet in Austin, Texas to an existing real estate venture (the “Austin Venture”) that the Company formed in 2013 with G&I VII Austin Office LLC, an investment vehicle advised by DRA Advisors LLC (“DRA”). The Company contributed the properties to the Austin Venture at an agreed upon value of $41.5 million. In conjunction with the contribution: (i) the Austin Venture obtained a $29.0 million mortgage loan; (ii) DRA contributed $5.9 million in net cash to the capital of the Austin Venture; and (iii) the Austin Venture distributed $34.4 million to the Company and credited the Company with a $5.9 million capital contribution to the Austin Venture. The Company incurred a $0.2 million loss on the contribution, driven primarily by closing costs.

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