Equity method investment summarized financial information debt.

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- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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- Definition

Amount of income (loss) for proportionate share of equity method investee's income (loss).

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Investment in Real Estate Ventures and Share of Real Estate Ventures' Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 11, 2018	Aug. 01, 2018	Jun. 26, 2018	May 29, 2015	Jul. 31, 2013
Schedule of Equity Method Investments [Line Items]
Carrying Amount	$ 120,294	$ 169,100	$ 194,621
Company's Share of Real Estate Venture Income (Loss)	(9,922)	(15,231)	$ (8,306)
Real Estate Venture Debt at 100%, gross	$ 596,007	$ 370,319
Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%	50.00%
Carrying Amount	$ 10,116	$ 11,731
Company's Share of Real Estate Venture Income (Loss)	(2,800)	(14,559)	$ (4,465)
Real Estate Venture Debt at 100%, gross	$ 0	26,111
Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage	15.00%
Carrying Amount	$ 16,446	47,834
Company's Share of Real Estate Venture Income (Loss)	(498)	83
Real Estate Venture Debt at 100%, gross	$ 207,302	$ 0
MAP Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%	50.00%
Carrying Amount	$ (70)	$ 11,173
Company's Share of Real Estate Venture Income (Loss)	(6,102)	(2,155)	$ (3,443)
Real Estate Venture Debt at 100%, gross	$ 185,000	185,000			$ 180,800
PJP VII
Schedule of Equity Method Investments [Line Items]
Ownership percentage	25.00%
Carrying Amount	$ 0	1,100
Company's Share of Real Estate Venture Income (Loss)	190	157
Real Estate Venture Debt at 100%, gross	$ 0	3,777
PJP Two
Schedule of Equity Method Investments [Line Items]
Ownership percentage	30.00%
Carrying Amount	$ 0	663
Company's Share of Real Estate Venture Income (Loss)	81	179
Real Estate Venture Debt at 100%, gross	$ 0	2,214
PJP VI
Schedule of Equity Method Investments [Line Items]
Ownership percentage	25.00%
Carrying Amount	$ 0	125
Company's Share of Real Estate Venture Income (Loss)	(185)	71
Real Estate Venture Debt at 100%, gross	$ 0	7,069
DRA Austin Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%
Carrying Amount	$ 0	0
Company's Share of Real Estate Venture Income (Loss)	0	1,687
Real Estate Venture Debt at 100%, gross	$ 0	0
1919 Ventures
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%					50.00%
Carrying Amount	$ 17,524	19,897
Company's Share of Real Estate Venture Income (Loss)	328	253
Real Estate Venture Debt at 100%, gross	$ 88,860	$ 88,860
Evo at Cira Centre South Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%	50.00%
Carrying Amount	$ 0	$ 0
Company's Share of Real Estate Venture Income (Loss)	0	(358)	$ 449
Real Estate Venture Debt at 100%, gross	$ 0	0
4040 Wilson Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%							50.00%
Carrying Amount	$ 37,002	37,371
Company's Share of Real Estate Venture Income (Loss)	(368)	(192)
Real Estate Venture Debt at 100%, gross	$ 114,845	57,288
JBG 51 N 50 Patterson
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%
Carrying Amount	$ 21,531	21,368
Company's Share of Real Estate Venture Income (Loss)	(313)	(137)
Real Estate Venture Debt at 100%, gross	$ 0	0
JBG 1250 First Street Office
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%						70.00%
Carrying Amount	$ 17,745	17,838
Company's Share of Real Estate Venture Income (Loss)	(255)	(260)
Real Estate Venture Debt at 100%, gross	$ 0	$ 0
DRA Austin Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage				50.00%
Percentage of ownership interests				50.00%