Brandywine Realty Trust (BDN) 10-K 22 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 15, 2019	Jun. 30, 2018
Entity Registrant Name	BRANDYWINE REALTY TRUST
Trading Symbol	BDN
Entity Central Index Key	790,816
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 2,970,155,345
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		175,813,097
Entity Small Business	false
Entity Shell Company	false
Entity Emerging Growth Company	false
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Entity Registrant Name	BRANDYWINE OPERATING PARTNERSHIP, L.P.
Entity Central Index Key	1,060,386
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Shell Company	false
Entity Emerging Growth Company	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Real estate investments:
Operating properties		$ 3,953,319	$ 3,832,348
Accumulated depreciation		(865,462)	(895,091)
Operating real estate investments, net		3,087,857	2,937,257
Construction-in-progress		150,263	121,188
Land held for development	[1]	86,401	98,242
Prepaid leasehold interests in land held for development, net	[2]	39,999	0
Total real estate investments, net		3,364,520	3,156,687
Assets held for sale, net		11,599	392
Cash and cash equivalents		22,842	202,179
Accounts receivable, net of allowance of $1,653 and $3,467 as of December 31, 2018 and December 31, 2017, respectively		16,394	17,938
Accrued rent receivable, net of allowance of $11,266 and $13,645 as of December 31, 2018 and December 31, 2017, respectively		165,243	169,760
Investment in Real Estate Ventures, equity method		169,100	194,621
Deferred costs, net		91,075	96,695
Intangible assets, net		131,348	64,972
Other assets		126,400	92,204
Total assets		4,098,521	3,995,448
LIABILITIES AND EQUITY
Mortgage notes payable, net		320,869	317,216
Unsecured credit facility		92,500	0
Unsecured term loan, net		248,042	248,429
Unsecured senior notes, net		1,366,635	1,365,183
Accounts payable and accrued expenses		125,696	107,074
Distributions payable		33,632	32,456
Deferred income, gains and rent		28,293	42,593
Acquired lease intangibles, net		31,783	20,274
Other liabilities		18,498	15,623
Total liabilities		2,265,948	2,148,848
Commitments and contingencies
Equity:
Common Shares of Brandywine Realty Trust's beneficial interest, $0.01 par value; shares authorized 400,000,000; 176,873,324 and 178,285,236 issued and outstanding as of December 31, 2018 and December 31, 2017, respectively		1,770	1,784
Additional paid-in-capital		3,200,850	3,218,564
Deferred compensation payable in common shares		14,021	12,445
Common shares in grantor trust, 977,120 and 894,736 issued and outstanding as of December 31, 2018 and December 31, 2017, respectively		(14,021)	(12,445)
Cumulative earnings		796,513	660,174
Accumulated other comprehensive income		5,029	2,399
Cumulative distributions		(2,183,909)	(2,053,741)
Total Brandywine Realty Trust's equity		1,820,253	1,829,180
Noncontrolling interests		12,320	17,420
Total beneficiaries' equity		1,832,573	1,846,600
Total liabilities and beneficiaries' equity		4,098,521	3,995,448
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Real estate investments:
Operating properties		3,953,319	3,832,348
Accumulated depreciation		(865,462)	(895,091)
Operating real estate investments, net		3,087,857	2,937,257
Construction-in-progress		150,263	121,188
Land held for development		86,401	98,242
Prepaid leasehold interests in land held for development, net		39,999	0
Total real estate investments, net		3,364,520	3,156,687
Assets held for sale, net		11,599	392
Cash and cash equivalents		22,842	202,179
Accounts receivable, net of allowance of $1,653 and $3,467 as of December 31, 2018 and December 31, 2017, respectively		16,394	17,938
Accrued rent receivable, net of allowance of $11,266 and $13,645 as of December 31, 2018 and December 31, 2017, respectively		165,243	169,760
Investment in Real Estate Ventures, equity method		169,100	194,621
Deferred costs, net		91,075	96,695
Intangible assets, net		131,348	64,972
Other assets		126,400	92,204
Total assets		4,098,521	3,995,448
LIABILITIES AND EQUITY
Mortgage notes payable, net		320,869	317,216
Unsecured credit facility		92,500
Unsecured term loan, net		248,042	248,429
Unsecured senior notes, net		1,366,635	1,365,183
Accounts payable and accrued expenses		125,696	107,074
Distributions payable		33,632	32,456
Deferred income, gains and rent		28,293	42,593
Acquired lease intangibles, net		31,783	20,274
Other liabilities		18,498	15,623
Total liabilities		2,265,948	2,148,848
Commitments and contingencies
Redeemable limited partnership units at redemption value; 1,479,799 and 1,535,102 issued and outstanding in 2016 and 2015, respectively		12,520	26,918
Equity:
General Partnership Capital; 176,873,324 and 178,285,236 units issued and outstanding as of December 31, 2018 and December 31, 2017, respectively		1,813,136	1,815,411
Accumulated other comprehensive income		4,725	2,056
Total Brandywine Operating Partnership, L.P.'s equity		1,817,861	1,817,467
Noncontrolling interest - consolidated real estate ventures		2,192	2,215
Total partners' equity		1,820,053	1,819,682
Total liabilities and beneficiaries' equity		$ 4,098,521	$ 3,995,448
[1]	As of December 31, 2018, the Company classified 37.9 acres of land held for development , comprised of 2.7 acres and 35.2 acres, located in its Pennsylvania Suburbs segment and Other segment, respectively, as held for sale in accordance with applicable accounting standards for long lived assets. See Note 3 , “Real Estate Investments,” for further information. As of December 31, 2017, the Company classified 13.1 acres of land held for development located in its Other segment as held for sale in accordance with applicable accounting standards for long lived assets.
[2]	As of December 31, 2018, this caption comprised leasehold interests in prepaid 99-year ground leases at 3025 and 3001-3003 JFK Boulevard, in Philadelphia, Pennsylvania. See Note 3, “Real Estate Investments

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable, allowance	$ 1,653	$ 3,467
Accrued rent receivable, allowance	$ 11,266	$ 13,645
Common Stock, Par or Stated Value Per Share (USD per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	400,000,000	400,000,000
Common Stock, Shares, Issued and Outstanding	176,873,324	178,285,236
Common Shares in Grantor Trust, Issued and Outstanding	977,120	894,736
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Accounts receivable, allowance	$ 1,653	$ 3,467
Accrued rent receivable, allowance	$ 11,266	$ 13,645
Redeemable Limited Partnership Units Issued and Outstanding	982,871	1,479,799
General Partners' Capital Account, Units Issued and Outstanding	176,873,324	178,285,236

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue
Total revenue	$ 544,345	$ 520,493	$ 525,463
Operating expenses:
Property operating expenses	154,772	150,835	152,926
Real estate taxes	51,341	45,204	46,252
Third party management expenses	11,910	9,960	10,270
Depreciation and amortization	174,259	179,357	189,676
General and administrative expenses	27,802	28,538	26,596
Provision for impairment	71,707	3,057	40,517
Total operating expenses	491,791	416,951	466,237
Gain on sale of real estate
Net gain on disposition of real estate	2,932	31,657	116,983
Net gain on sale of undepreciated real estate	3,040	953	9,232
Total gain on sale of real estate	5,972	32,610	126,215
Operating income	58,526	136,152	185,441
Other income (expense):
Interest income	4,703	1,113	1,236
Interest expense	(78,199)	(81,886)	(84,708)
Interest expense - amortization of deferred financing costs	(2,498)	(2,435)	(2,696)
Interest expense - financing obligation	0	0	(679)
Equity in loss of Real Estate Ventures	(15,231)	(8,306)	(11,503)
Net gain on real estate venture transactions	142,233	80,526	20,000
Gain on promoted interest in unconsolidated real estate venture	28,283	0	0
Loss on early extinguishment of debt	(105)	(3,933)	(66,590)
Net income before income taxes	137,712	121,231	40,501
Income tax (provision) benefit	(423)	628	0
Net income	137,289	121,859	40,501
Net income attributable to noncontrolling interests	(965)	(1,009)	(310)
Net income attributable to Brandywine Realty Trust	136,324	120,850	40,191
Distribution to preferred shareholders	0	(2,032)	(6,900)
Preferred share redemption charge	0	(3,181)	0
Nonforfeitable dividends allocated to unvested restricted shareholders	(369)	(327)	(341)
Net income attributable to Common Shareholders of Brandywine Realty Trust	$ 135,955	$ 115,310	$ 32,950
Basic income per Common Share	$ 0.76	$ 0.66	$ 0.19
Diluted income per Common Share	$ 0.76	$ 0.65	$ 0.19
Basic weighted average shares outstanding	178,519,748	175,484,350	175,018,163
Diluted weighted average shares outstanding	179,641,492	176,808,166	176,010,814
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Total revenue	$ 544,345	$ 520,493	$ 525,463
Operating expenses:
Property operating expenses	154,772	150,835	152,926
Real estate taxes	51,341	45,204	46,252
Third party management expenses	11,910	9,960	10,270
Depreciation and amortization	174,259	179,357	189,676
General and administrative expenses	27,802	28,538	26,596
Provision for impairment	71,707	3,057	40,517
Total operating expenses	491,791	416,951	466,237
Gain on sale of real estate
Net gain on disposition of real estate	2,932	31,657	116,983
Net gain on sale of undepreciated real estate	3,040	953	9,232
Total gain on sale of real estate	5,972	32,610	126,215
Operating income	58,526	136,152	185,441
Other income (expense):
Interest income	4,703	1,113	1,236
Interest expense	(78,199)	(81,886)	(84,708)
Interest expense - amortization of deferred financing costs	(2,498)	(2,435)	(2,696)
Interest expense - financing obligation	0	0	(679)
Equity in loss of Real Estate Ventures	(15,231)	(8,306)	(11,503)
Net gain on real estate venture transactions	142,233	80,526	20,000
Gain on promoted interest in unconsolidated real estate venture	28,283	0	0
Loss on early extinguishment of debt	(105)	(3,933)	(66,590)
Net income before income taxes	137,712	121,231	40,501
Income tax (provision) benefit	(423)	628	0
Net income	137,289	121,859	40,501
Net income attributable to noncontrolling interests - consolidated real estate ventures	(55)	(29)	(15)
Distribution to preferred shareholders	0	(2,032)	(6,900)
Preferred share redemption charge	0	(3,181)	0
Nonforfeitable dividends allocated to unvested restricted shareholders	(369)	(327)	(341)
Net income attributable to Common Shareholders of Brandywine Realty Trust	136,865	116,290	33,245
Net income attributable to Brandywine Operating Partnership	137,234	121,830	40,486
Distribution to preferred unitholders	0	(2,032)	(6,900)
Preferred unit redemption charge	0	(3,181)	0
Nonforfeitable dividends allocated to unvested restricted unitholders	$ (369)	$ (327)	$ (341)
Basic income per Common Share	$ 0.76	$ 0.66	$ 0.19
Diluted income per Common Share	$ 0.76	$ 0.65	$ 0.19
Basic weighted average shares outstanding	179,959,370	176,964,149	176,523,800
Diluted weighted average shares outstanding	181,081,114	178,287,965	177,516,451
Rents [Member]
Revenue
Lease revenue	$ 430,656	$ 412,333	$ 421,505
Rents [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Lease revenue	430,656	412,333	421,505
Tenant Reimbursements [Member]
Revenue
Service and other revenue	82,625	72,620	70,629
Tenant Reimbursements [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Service and other revenue	82,625	72,620	70,629
Termination Fees [Member]
Revenue
Lease revenue	1,763	2,370	2,339
Termination Fees [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Lease revenue	1,763	2,370	2,339
Third Party Management Fees, Labor Reimbursement and Leasing [Member]
Revenue
Service and other revenue	22,557	28,345	26,674
Third Party Management Fees, Labor Reimbursement and Leasing [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Service and other revenue	22,557	28,345	26,674
Other [Member]
Revenue
Service and other revenue	6,744	4,825	4,316
Other [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Service and other revenue	$ 6,744	$ 4,825	$ 4,316

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income		$ 137,289	$ 121,859	$ 40,501
Comprehensive income:
Unrealized gain on derivative financial instruments		1,478	2,948	2,371
Amortization of interest rate contracts	[1]	1,191	1,230	1,104
Total comprehensive income		2,669	4,178	3,475
Comprehensive income		139,958	126,037	43,976
Comprehensive income attributable to noncontrolling interest		(1,004)	(1,043)	(338)
Comprehensive income attributable to Brandywine Realty Trust/Brandywine Operating Partnership		138,954	124,994	43,638
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Net income		137,289	121,859	40,501
Comprehensive income:
Unrealized gain on derivative financial instruments		1,478	2,948	2,371
Amortization of interest rate contracts	[2]	1,191	1,230	1,104
Total comprehensive income		2,669	4,178	3,475
Comprehensive income		139,958	126,037	43,976
Comprehensive income attributable to noncontrolling interest		(55)	(29)	(15)
Comprehensive income attributable to Brandywine Realty Trust/Brandywine Operating Partnership		$ 139,903	$ 126,008	$ 43,961
[1]	Amounts reclassified from comprehensive income to interest expense within the Consolidated Statements of Operations.
[2]	Amounts reclassified from comprehensive income to interest expense within the Consolidated Statement of Operations.

Consolidated Statements of Bene

Consolidated Statements of Beneficiaries' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Deferred Compensation, Share-based Payments [Member]	Additional Paid-in Capital [Member]	Common Stock In Grantor Trust [Member]	Cumulative Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Cumulative Distributions [Member]	Noncontrolling Interest [Member]
Beginning Balance at Dec. 31, 2015	$ 1,952,091	$ 40	$ 1,747	$ 11,918	$ 3,252,622			$ (5,192)	$ (1,814,378)	$ 18,166
Beginning Balance, Shares at Dec. 31, 2015		4,000,000	174,688,568	745,686		(11,918)	499,086
Net income	40,501						$ 40,191			310
Other comprehensive income	3,475							3,447		28
Issuance of partnership interest in consolidated real estate venture	108									108
Conversion of LP Units to Common Shares	$ 0		$ 1		874					(875)
Conversion of LP Units to Common Shares, Shares			55,303
Repurchase and retirement of Common Shares of Beneficial Interest, Shares	0
Share-based compensation activity	$ 5,764		$ 4		5,718		42
Share-based compensation activity, Shares			405,200
Share Issuance from/(to) Deferred Compensation Plan	(47)			$ 1,766	(47)	$ (1,766)
Share Issuance from/(to) Deferred Compensation Plan, Shares			(8,311)	153,771
Reallocation of Noncontrolling Interest	0				(297)					297
Preferred Share distributions	(6,900)								(6,900)
Distributions declared	(111,555)								(110,614)	(941)
Ending Balance at Dec. 31, 2016	1,883,437	$ 40	$ 1,752	$ 13,684	3,258,870	(13,684)	539,319	(1,745)	(1,931,892)	17,093
Ending Balance, Shares at Dec. 31, 2016		4,000,000	175,140,760	899,457
Net income	121,859						120,850			1,009
Other comprehensive income	4,178							4,144		34
Issuance of partnership interest in consolidated real estate venture	85									85
Conversion of LP Units to Common Shares, Shares			2,858,991
Issuance of Common Shares of Beneficial Interest	51,225		$ 29		51,196
Redemption of Preferred Shares	$ (96,850)	$ (40)			(96,810)
Redemption of Preferred Shares, Shares		(4,000,000)
Repurchase and retirement of Common Shares of Beneficial Interest, Shares	0
Distributions from consolidated real estate ventures	$ (48)									(48)
Equity issuance costs	(499)				(499)
Bonus share issuance	110				110
Share-based compensation activity	6,697		$ 3		6,689		5
Share-based compensation activity, Shares			333,127	39,870
Share Issuance from/(to) Deferred Compensation Plan	$ (768)			$ (1,239)	(768)	1,239
Share Issuance from/(to) Deferred Compensation Plan, Shares			(52,971)	(44,591)
Share Choice Plan Issuance, Shares	0		(1,423)
Reallocation of Noncontrolling Interest	$ 0				(224)					224
Preferred Share distributions	(2,032)								(2,032)
Preferred Share redemption charges	(3,181)								(3,181)
Distributions declared	(117,613)								(116,636)	(977)
Ending Balance at Dec. 31, 2017	1,846,600	$ 0	$ 1,784	$ 12,445	3,218,564	(12,445)	660,174	2,399	(2,053,741)	17,420
Ending Balance, Shares at Dec. 31, 2017		0	178,285,236	894,736
Bonus share issuance, Shares			6,752
Net income	137,289						136,324			965
Other comprehensive income	2,669							2,630		39
Issuance of partnership interest in consolidated real estate venture	16									16
Conversion of LP Units to Common Shares, Shares			23,311
Issuance of Common Shares of Beneficial Interest	416				416
Repurchase and retirement of Common Shares of Beneficial Interest	$ (21,858)		$ (17)		(21,841)
Repurchase and retirement of Common Shares of Beneficial Interest, Shares	(1,729,278)		(1,729,278)
Distributions from consolidated real estate ventures	$ (94)									(94)
Redemption of LP Units	(7,043)									(7,043)
Share-based compensation activity	5,843		$ 2		5,826		15
Share-based compensation activity, Shares			196,151
Share Issuance from/(to) Deferred Compensation Plan	$ (111)		$ 1	$ 1,576	(112)	(1,576)
Share Issuance from/(to) Deferred Compensation Plan, Shares			99,189	82,384
Share Choice Plan Issuance, Shares	0		(1,285)
Reallocation of Noncontrolling Interest	$ 0				(2,003)					2,003
Preferred Share distributions	0
Distributions declared	(131,154)								(130,168)	(986)
Ending Balance at Dec. 31, 2018	$ 1,832,573	$ 0	$ 1,770	$ 14,021	$ 3,200,850	$ (14,021)	$ 796,513	$ 5,029	$ (2,183,909)	$ 12,320
Ending Balance, Shares at Dec. 31, 2018		0	176,873,324	977,120

Consolidated Statements of Be_2

Consolidated Statements of Beneficiaries' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Stockholders Equity [Abstract]
Distributions declared per Common Share	$ 0.73	$ 0.66	$ 0.63

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 137,289	$ 121,859	$ 40,501
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	174,259	179,357	189,676
Amortization of deferred financing costs	2,498	2,435	2,696
Amortization of debt discount/(premium), net	702	1,569	1,471
Amortization of stock compensation costs	5,716	4,883	4,310
Straight-line rent income	(12,283)	(27,115)	(28,351)
Amortization of acquired above (below) market leases, net	(3,344)	(3,071)	(6,529)
Straight-line ground rent expense	355	88	88
Provision for doubtful accounts	1,775	2,207	1,865
Net gain on real estate venture transactions	(142,233)	(80,526)	(20,000)
Gain on promoted interest	(28,283)	0	0
Net gain on sale of interests in real estate	(5,972)	(32,610)	(126,215)
Loss on early extinguishment of debt	105	3,933	66,590
Provision for impairment	71,707	3,057	40,517
Other than temporary impairment	4,076	4,844	0
Loss from Real Estate Ventures, net of distributions	12,871	3,462	12,125
Deferred financing obligation	0	0	(679)
Income tax benefit (provision)	423	(628)	0
Changes in assets and liabilities:
Accounts receivable	3,524	(6,266)	2,373
Other assets	(14,334)	1,752	544
Accounts payable and accrued expenses	12,579	4,004	(8,004)
Deferred income, gains and rent	3,017	(1,482)	137
Other liabilities	2,902	829	685
Net cash provided by operating activities	227,349	182,581	173,800
Cash flows from investing activities:
Acquisition of properties	(196,625)	(72,523)	(20,406)
Proceeds from the sale of properties	324,090	171,860	784,331
Proceeds from real estate venture sales	60,346	145,416	21,022
Issuance of mortgage notes receivable	(175,172)	0	(3,380)
Proceeds from repayment of mortgage notes receivable	192	151	0
Proceeds from repayment of a capital lease	181	0	0
Capital expenditures for tenant improvements	(65,264)	(60,586)	(51,398)
Capital expenditures for redevelopments	(48,231)	(34,679)	(11,909)
Capital expenditures for developments	(99,104)	(66,915)	(191,184)
Advances for the purchase of tenant assets, net of repayments	410	18	(784)
Investment in unconsolidated Real Estate Ventures	(908)	(6,638)	(28,610)
Deposits for real estate	(8,234)	573	(746)
Escrowed cash	5,694	0	6,992
Capital distributions from Real Estate Ventures	6,526	20,781	13,065
Leasing costs paid	(18,407)	(17,657)	(16,083)
Net cash (used in) provided by investing activities	(214,506)	79,801	500,910
Cash flows from financing activities:
Proceeds from mortgage notes payable	0	0	86,900
Repayments of mortgage notes payable	(122,180)	(4,931)	(357,151)
Proceeds from credit facility borrowings	455,500	341,000	195,000
Repayments of credit facility borrowings	(363,000)	(341,000)	(195,000)
Proceeds from unsecured notes	0	550,131	0
Repayments of unsecured notes	0	(628,590)	(149,919)
Debt financing costs paid	(3,430)	(4,727)	(495)
Redemption of preferred shares	0	(100,000)	0
Proceeds from the exercise of stock options	0	1,229	1,286
Proceeds from the issuance of common shares	416	51,225	0
Shares used for employee taxes upon vesting of share awards	(1,494)	(674)	(879)
Partner contributions to consolidated real estate venture	16	85	108
Partner distributions from consolidated real estate venture	(94)	(48)	0
Repurchase and retirement of common shares	(21,841)	0	0
Redemption of limited partnership units	(7,043)	0	0
Distributions paid to shareholders	(128,859)	(116,311)	(115,702)
Distributions to noncontrolling interest	(1,065)	(947)	(934)
Net cash used in financing activities	(193,074)	(253,558)	(536,786)
Decrease in cash and cash equivalents and restricted cash	(180,231)	8,824	137,924
Cash and cash equivalents and restricted cash at beginning of year	203,442	194,618	56,694
Cash and cash equivalents and restricted cash at end of period	23,211	203,442	194,618
Supplemental disclosure:
Cash paid for interest, net of capitalized interest during the twelve months ended December 31, 2018, 2017 and of $3,586, $3,527 and $12,835, respectively	76,858	83,139	97,843
Cash paid for income taxes	405	225	0
Supplemental disclosure of non-cash activity:
Dividends and distributions declared but not paid	33,632	32,456	30,032
Change in construction-in-progress related to non-cash disposition of land	27,231	0	0
Change in deferred income, gains and rent to the non-cash disposition of land	(29,780)	0	0
Change in investment in real estate ventures as a result of dispositions	14,169	(64,792)	(2,023)
Change in Notes receivable as a result of a noncash acquisition of an operating property	130,742	0	25,165
Change in real estate ventures as a result of other than temporary impairment	(4,076)	(4,844)	0
Change in operating real estate from deconsolidation of 3141 Fairview Park Drive	0	0	44,313
Change in investment in real estate ventures from deconsolidation of 3141 Fairview Park Drive	0	0	(12,642)
Change in mortgage notes payable from deconsolidation of 3141 Fairview Park Drive	0	0	(20,582)
Change in other liabilities from deconsolidation of 3141 Fairview Park Drive	0	0	(12,384)
Change in operating real estate related to a non-cash acquisition of an operating property	(20,653)	0	0
Change in intangible assets, net related to non-cash acquisition of an operating property	(3,144)	0	0
Change in acquired lease intangibles, net related to non-cash acquisition of an operating property	182	0	0
Change in investments in joint venture related to non-cash acquisition of property	(16,832)	0	0
Change in mortgage notes payable related to acquisition of an operating property	9,940	0	0
Change in capital expenditures financed through accounts payable at period end	8,784	(6,593)	8,222
Change in capital expenditures financed through retention payable at period end	(2,912)	(159)	848
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Cash flows from operating activities:
Net income	137,289	121,859	40,501
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	174,259	179,357	189,676
Amortization of deferred financing costs	2,498	2,435	2,696
Amortization of debt discount/(premium), net	702	1,569	1,471
Amortization of stock compensation costs	5,716	4,883	4,310
Straight-line rent income	(12,283)	(27,115)	(28,351)
Amortization of acquired above (below) market leases, net	(3,344)	(3,071)	(6,529)
Straight-line ground rent expense	355	88	88
Provision for doubtful accounts	1,775	2,207	1,865
Net gain on real estate venture transactions	(142,233)	(80,526)	(20,000)
Gain on promoted interest	(28,283)	0	0
Net gain on sale of interests in real estate	(5,972)	(32,610)	(126,215)
Loss on early extinguishment of debt	105	3,933	66,590
Provision for impairment	71,707	3,057	40,517
Other than temporary impairment	4,076	4,844	0
Loss from Real Estate Ventures, net of distributions	12,871	3,462	12,125
Deferred financing obligation	0	0	(679)
Income tax benefit (provision)	423	(628)	0
Changes in assets and liabilities:
Accounts receivable	3,524	(6,266)	2,373
Other assets	(14,334)	1,752	544
Accounts payable and accrued expenses	12,579	4,004	(8,004)
Deferred income, gains and rent	3,017	(1,482)	137
Other liabilities	2,902	829	685
Net cash provided by operating activities	227,349	182,581	173,800
Cash flows from investing activities:
Acquisition of properties	(196,625)	(72,523)	(20,406)
Proceeds from the sale of properties	324,090	171,860	784,331
Proceeds from real estate venture sales	60,346	145,416	21,022
Issuance of mortgage notes receivable	(175,172)	0	(3,380)
Proceeds from repayment of mortgage notes receivable	192	151	0
Proceeds from repayment of a capital lease	181	0	0
Capital expenditures for tenant improvements	(65,264)	(60,586)	(51,398)
Capital expenditures for redevelopments	(48,231)	(34,679)	(11,909)
Capital expenditures for developments	(99,104)	(66,915)	(191,184)
Advances for the purchase of tenant assets, net of repayments	410	18	(784)
Investment in unconsolidated Real Estate Ventures	(908)	(6,638)	(28,610)
Deposits for real estate	(8,234)	573	(746)
Escrowed cash	5,694	0	6,992
Capital distributions from Real Estate Ventures	6,526	20,781	13,065
Leasing costs paid	(18,407)	(17,657)	(16,083)
Net cash (used in) provided by investing activities	(214,506)	79,801	500,910
Cash flows from financing activities:
Proceeds from mortgage notes payable	0	0	86,900
Repayments of mortgage notes payable	(122,180)	(4,931)	(357,151)
Proceeds from credit facility borrowings	455,500	341,000	195,000
Repayments of credit facility borrowings	(363,000)	(341,000)	(195,000)
Proceeds from unsecured notes	0	550,131	0
Repayments of unsecured notes	0	(628,590)	(149,919)
Debt financing costs paid	(3,430)	(4,727)	(495)
Redemption of preferred shares	0	(100,000)	0
Proceeds from the exercise of stock options	0	1,229	1,286
Proceeds from the issuance of common shares	416	51,225	0
Shares used for employee taxes upon vesting of share awards	(1,494)	(674)	(879)
Partner contributions to consolidated real estate venture	16	85	108
Partner distributions from consolidated real estate venture	(94)	(48)	0
Repurchase and retirement of common shares	(21,841)	0	0
Redemption of limited partnership units	(7,043)	0	0
Distributions paid to shareholders	(129,924)	(117,258)	(116,636)
Net cash used in financing activities	(193,074)	(253,558)	(536,786)
Decrease in cash and cash equivalents and restricted cash	(180,231)	8,824	137,924
Cash and cash equivalents and restricted cash at beginning of year	203,442	194,618	56,694
Cash and cash equivalents and restricted cash at end of period	23,211	203,442	194,618
Supplemental disclosure:
Cash paid for interest, net of capitalized interest during the twelve months ended December 31, 2018, 2017 and of $3,586, $3,527 and $12,835, respectively	76,858	83,139	97,843
Cash paid for income taxes	405	225	0
Supplemental disclosure of non-cash activity:
Dividends and distributions declared but not paid	33,632	32,456	30,032
Change in construction-in-progress related to non-cash disposition of land	27,231	0	0
Change in deferred income, gains and rent to the non-cash disposition of land	(29,780)	0	0
Change in investment in real estate ventures as a result of dispositions	14,169	(64,792)	(2,023)
Change in Notes receivable as a result of a noncash acquisition of an operating property	130,742	0	25,162
Change in real estate ventures as a result of other than temporary impairment	(4,076)	(4,844)	0
Change in operating real estate from deconsolidation of 3141 Fairview Park Drive	0	0	44,313
Change in investment in real estate ventures from deconsolidation of 3141 Fairview Park Drive	0	0	(12,642)
Change in mortgage notes payable from deconsolidation of 3141 Fairview Park Drive	0	0	(20,582)
Change in other liabilities from deconsolidation of 3141 Fairview Park Drive	0	0	(12,384)
Change in operating real estate related to a non-cash acquisition of an operating property	(20,653)	0	0
Change in intangible assets, net related to non-cash acquisition of an operating property	(3,144)	0	0
Change in acquired lease intangibles, net related to non-cash acquisition of an operating property	182	0	0
Change in investments in joint venture related to non-cash acquisition of property	(16,832)	0	0
Change in mortgage notes payable related to acquisition of an operating property	9,940	0	0
Change in capital expenditures financed through accounts payable at period end	8,784	(6,593)	8,222
Change in capital expenditures financed through retention payable at period end	$ (2,912)	$ (159)	$ 848

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Capitalized interest	$ 3,586	$ 3,527	$ 12,835
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Capitalized interest	$ 3,586	$ 3,527	$ 12,835

Consolidated Statements of Part

Consolidated Statements of Partners' Equity - USD ($) $ in Thousands	Total	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P.	BRANDYWINE OPERATING PARTNERSHIP, L.P.General Partner Capital [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P.Series E-linked Preferred Stock [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P.Accumulated Other Comprehensive Income (Loss) [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P.Noncontrolling Interest [Member]
Beginning Balance at Dec. 31, 2015				$ 1,929,977	$ 1,836,692	$ 96,850	$ (5,597)	$ 2,032
Beginning Balance, Shares at Dec. 31, 2015					174,688,568	4,000,000
Net income	$ 40,501		$ 310	40,501	$ 40,486			15
Other comprehensive income	3,475	$ 3,447	28	3,475			3,475
Share Issuance from/(to) Deferred Compensation Plan	(47)			(47)	$ (47)
Share Issuance from/(to) Deferred Compensation Plan, Shares					(8,311)
Issuance of partnership interest in consolidated real estate venture	108		108	109				109
Conversion of LP Units to Common Shares	0		(875)	875	$ 875
Conversion of LP Units to Common Shares, Shares					55,303
Share-based compensation activity	5,764			5,763	$ 5,763
Share-based compensation activity, Shares					405,200
Adjustment of redeemable partnership units to liquidation value at period end				(2,622)	$ (2,622)
Reallocation of Noncontrolling Interest	0		297	0	6			(6)
Redemption value of limited partnership units				(875)	(875)
Preferred Share distributions	(6,900)			(6,900)	(6,900)
Preferred share redemption charge	0			0
Distributions declared to general partnership unitholders				(110,614)	(110,614)
Ending Balance at Dec. 31, 2016				1,859,642	$ 1,762,764	$ 96,850	(2,122)	2,150
Ending Balance, Shares at Dec. 31, 2016					175,140,760	4,000,000
Net income	121,859		1,009	121,859	$ 121,830			29
Other comprehensive income	4,178	4,144	34	4,178			4,178
Redemption of Preferred Mirror Units				(96,850)		$ (96,850)
Redemption of Preferred Mirror Units, Shares						(4,000,000)
Share Issuance from/(to) Deferred Compensation Plan	(768)			(768)	$ (768)
Share Issuance from/(to) Deferred Compensation Plan, Shares					(52,971)
Issuance of LP Units				50,726	$ 50,726
Issuance of LP Units, Shares					2,858,991
Issuance of partnership interest in consolidated real estate venture	85		85	85				85
Distributions from consolidated real estate ventures	$ (48)		(48)	$ (48)				(48)
Share Choice Plan Issuance, Shares	0			0	(1,423)
Bonus share issuance	$ 110			$ 110	$ 110
Bonus share issuance, Shares					6,752
Share-based compensation activity	6,697			6,697	$ 6,697
Share-based compensation activity, Shares					333,127
Adjustment of redeemable partnership units to liquidation value at period end				(4,100)	$ (4,099)			(1)
Reallocation of Noncontrolling Interest	0		224
Preferred Share distributions	(2,032)			(2,032)	(2,032)
Preferred share redemption charge	(3,181)			(3,181)	(3,181)
Distributions declared to general partnership unitholders				(116,636)	(116,636)
Ending Balance at Dec. 31, 2017				1,819,682	$ 1,815,411	$ 0	2,056	2,215
Ending Balance, Shares at Dec. 31, 2017					178,285,236	0
Net income	137,289		965	137,289	$ 137,234			55
Other comprehensive income	2,669	$ 2,630	39	2,669			2,669
Share Issuance from/(to) Deferred Compensation Plan	(111)			(111)	$ (111)
Share Issuance from/(to) Deferred Compensation Plan, Shares					99,189
Issuance of LP Units				416	$ 416
Issuance of LP Units, Shares					23,311
Repurchase and retirement of LP units				(21,858)	$ (21,858)
Repurchase and retirement of LP units, Shares					(1,729,278)
Issuance of partnership interest in consolidated real estate venture	16		16	16				16
Distributions from consolidated real estate ventures	$ (94)		(94)	$ (94)				(94)
Share Choice Plan Issuance, Shares	0			0	(1,285)
Share-based compensation activity	$ 5,843			$ 5,843	$ 5,843
Share-based compensation activity, Shares					196,151
Reallocation of Noncontrolling Interest	0		$ 2,003
Redemption value of limited partnership units				6,369	$ 6,369
Preferred Share distributions	0			0
Preferred share redemption charge	$ 0			0
Distributions declared to general partnership unitholders				(130,168)	(130,168)
Ending Balance at Dec. 31, 2018				$ 1,820,053	$ 1,813,136	$ 0	$ 4,725	$ 2,192
Ending Balance, Shares at Dec. 31, 2018					176,873,324	0

Consolidated Statements of Pa_2

Consolidated Statements of Partners' Equity (Parenthetical) - BRANDYWINE OPERATING PARTNERSHIP, L.P. - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Distributions to general partnership unitholders (USD per share)	$ 0.73	$ 0.66	$ 0.63
General Partner Capital [Member]
Distributions to general partnership unitholders (USD per share)	$ 0.73	$ 0.66	$ 0.63

Organization of the Parent Comp

Organization of the Parent Company and The Operating Partnership	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP	1. ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP The Parent Company is a self-administered and self-managed real estate investment trust (“REIT”) that provides leasing, property management, development, redevelopment, acquisition and other tenant-related services for a portfolio of office, retail and mixed-use properties. The Parent Company owns its assets and conducts its operations through the Operating Partnership and subsidiaries of the Operating Partnership. The Parent Company is the sole general partner of the Operating Partnership and, as of December 31, 2018, owned a 99.4% interest in the Operating Partnership. The Parent Company’s common shares of beneficial interest are publicly traded on the New York Stock Exchange under the ticker symbol “BDN.” As of December 31, 2018 97 16.8 one three Number of Properties Rentable Square Feet Office properties 88 15,609,156 Mixed-use properties 4 646,741 Retail property 1 17,884 Core Properties 93 16,273,781 Development property 1 164,818 Redevelopment properties 3 338,650 The Properties 97 16,777,249 In addition to the Properties, a s of December 31, , the Company owned land held for development, comprised of 237.4 acres of undeveloped land, of which 37.9 acres were held for sale, 1.8 acres related to leasehold interests in two land parcels, each acquired through prepaid 99-year “Investment in Unconsolidated Real Estate Ventures,” for further information). The Properties and the properties owned by the Real Estate Ventures are located in or near Philadelphia, Pennsylvania; Austin, Texas; Metropolitan Washington, D.C.; Southern New Jersey; and Wilmington, Delaware. All references to building square footage, rentable square feet, acres, occupancy percentage the number of buildings and tax basis are unaudited. The Company conducts its third-party real estate management services business primarily through six management companies (collectively, the “Management Companies”): Brandywine Realty Services Corporation (“BRSCO”), BDN Management Holdings, LLC (“BMH”), Brandywine Properties I Limited, Inc. (“BPI”), BDN Brokerage, LLC (“BBL”), Brandywine Properties Management, L.P. (“BPM”) and Brandywine Brokerage Services, LLC (“BBS”). BRSCO, BMH and BPI are each a taxable REIT subsidiary. As of December 31, 2018, the Operating Partnership owned, directly and indirectly, 100% of each of BRSCO, BMH, BPI, BBL, BPM and BBS. As of December 31, 2018, the Management Company subsidiaries were managing properties containing an aggregate of approximately 24.8 million net rentable square feet, of which approximately 16.8 million net rentable square feet related to Properties owned by the Company and approximately 8.0 million net rentable square feet related to properties owned by third parties and Real Estate Ventures.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Out of Period Adjustment The Company recorded $1.2 million of impairment charges during the quarter ended December 31, 2016, which should have been recorded in the consolidated financial statements for the three-month period ended March 31, 2017 and the year ended December 31, 2017. Management concluded that this misstatement was not material to any prior period, nor was it material to the consolidated financial statements as of and for the twelve-month periods ended December 31, 2017 and 2016. Reclassifications and Adoption of New Accounting Guidance Through the year ended December 31, 2017, the Company included $0.6 million of income tax benefit in general and administrative expenses. During the fourth quarter of 2017, the Company began disaggregating the income tax provision/benefit in the consolidated statements of operations. As a result, in the statements of operations for the year ended December 31, 2017 the Company reclassified $0.6 million of net income tax benefit out of general and administrative expenses into the “Income tax (provision) benefit” caption in the consolidated statements of operations to provide comparative presentation. During the first quarter of 2018, the Company adopted Financial Accounting Standards Board (the “FASB”) Accounting Standards Update (“ASU”) No. 2016-18, which requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents and amounts described as restricted cash or cash equivalents. Beginning-of-period and end-of-period total amounts shown on the statement of cash flows should include restricted 0.4 1.3 1.3 . I n accordance with ASC 360, and in response to the SEC’s “Disclosure Update and Simplification” release effective November 5, 2018, the Company reclassified gains and losses resulting from wholly owned real estate dispositions from the “Other income (expense)” section to the “Operating income” section within its consolidated statements of operations. As a result, in the consolidated statements of operations for the years ended December 31, 2018, 2017 and 2016, the Company reclassified the following amounts to the “Operating income” section: Caption 2018 2017 2016 Net gain on disposition of real estate $ 2,932 $ 31,657 $ 116,983 Net gain on sale of undepreciated real estate 3,040 953 9,232 Total gain on sale of real estate $ 5,972 $ 32,610 $ 126,215 Principles of Consolidation The Company consolidates variable interest entities (“VIEs”) in which it is considered to be the primary beneficiary. VIEs are entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or that the holders of the equity investment at risk do not have a controlling financial interest. The primary beneficiary is defined by the entity having both of the following characteristics: (i) the power to direct those matters that most significantly impact the activities of the VIE and (ii) the obligation to absorb losses or the right to receive benefits of the VIE that could potentially be significant to the VIE. For entities that the Company has the obligations to fund losses, its maximum exposure to loss is not limited to the carrying amount of its investments. When an entity is not deemed to be a VIE, the Company consolidates entities for which it has significant decision making control over the entity’s operations. The Company’s judgement with respect to its level of influence or control of an entity involves consideration of various factors including the form of the Company’s ownership interest, its representation in the entity’s governance, the size of its investment (including loans), estimates of future cash flows, its ability to participate in policy making decisions and the rights of the other investors to participate in the decision making process and to replace the Company as manager and/or liquidate the venture, if applicable. The Company’s assessment of its influence or control over an entity affects the presentation of these investments in the Company’s consolidated financial statements. In addition to evaluating control rights, the Company consolidates entities in which the outside partner has no substantive kick-out rights to remove the Company as managing member. The portion of the consolidated entities that are not owned by the Company is presented as noncontrolling interest as of and during the periods consolidated. All intercompany transactions have been eliminated in consolidation. The Company continuously assesses its determination of the primary beneficiary for each entity and assesses reconsideration events that may cause a change in the original determinations . As of December 31, 2018 and 2017, the Company included in its consolidated balance sheets consolidated VIEs having total assets of $414.3 million and $412.9 million, respectively, and total liabilities of $254.1 million and $250.4 million, respectively. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates. Management makes significant estimates regarding revenue, valuation of real estate and related intangible assets and liabilities, impairment of long-lived assets, impairment of investments in Real Estate Ventures allowance for doubtful accounts, variable employee compensation, deferred costs and contingencies. Operating Properties Operating properties are carried at historical cost less accumulated depreciation and impairment losses. The value of operating properties reflects their purchase price or development cost. Acquisition costs related to business combinations are expensed as incurred, whereas the costs related to asset acquisitions are capitalized as incurred. Costs incurred for the renovation and betterment of an operating property are capitalized to the Company’s investment in that property. Ordinary repairs and maintenance are expensed as incurred. Purchase Price Allocation For acquisitions of real estate or in-substance real estate that are accounted for as business combinations, we recognize the assets acquired (including the intangible value of acquired above- or below-market leases, acquired in-place leases and tenant relationship values), liabilities assumed, noncontrolling interests, and previously existing ownership interests at fair value as of the acquisition date. Any excess (deficit) of the consideration transferred relative to the fair value of the net assets acquired is accounted for as goodwill (bargain purchase gain). Acquisition costs related to business combinations are expensed as incurred. Acquisitions of real estate and in-substance real estate that do not meet the definition of a business are accounted for as asset acquisitions. The accounting model for asset acquisitions is similar to the accounting model for business combinations except that the acquisition consideration (including acquisition costs) is allocated to the individual assets acquired and liabilities assumed on a relative fair value basis. As a result, asset acquisitions do not result in recognition of goodwill or a bargain purchase gain. Additionally, because the accounting model for asset acquisitions is a cost accumulation model, preexisting interests in the acquired assets, if any, are not remeasured to fair value but continue to be accounted for at their historical cost. Direct acquisition costs are capitalized if an asset acquisition is probable. If we determine that an asset acquisition is no longer probable, no new costs are capitalized and all capitalized costs that are not recoverable are written off. The Company adopted ASU 2017-01 – Business Combinations as of January 1, 2017, which amended the definition of a business. The purchase price is allocated to the acquired assets and assumed liabilities, including land and buildings, as if vacant based on highest and best use for the acquired assets. The Company assesses and considers fair value of the operating properties based on estimated cash flow projections that utilize discount and/or capitalization rates that it deems appropriate, as well as available market information. Estimates of future cash flows are based on a number of factors including the historical operating results, known and anticipated trends, and market and economic conditions. The Company allocates the purchase price of properties considered to be business combinations and asset acquisitions to net tangible and identified intangible assets acquired based on fair values. Above-market and below-market in-place lease values for acquired properties are recorded based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to the in-place leases and (ii) the Company’s estimate of the fair market lease rates for the corresponding in-place leases, measured over a period equal to the remaining non-cancelable term of the lease (including the below market fixed renewal period, if applicable). Capitalized above-market lease values are amortized as a reduction of rental income over the remaining non-cancelable terms of the respective leases. Capitalized below-market lease values are amortized as an increase to rental income over the remaining non-cancelable terms of the respective leases, including any below market fixed-rate renewal option periods that are considered probable. Other intangible assets also include in-place leases based on the Company’s evaluation of the specific characteristics of each tenant’s lease and the Company’s overall relationship with the respective tenant. The Company estimates the cost to execute leases with terms similar to the remaining lease terms of the in-place leases, including leasing commissions, legal and other related expenses. This intangible asset is amortized to expense over the remaining term of the respective leases and any fixed-rate bargain renewal periods. Company estimates of value are made using methods similar to those used by independent appraisers or by using independent appraisals. Factors considered by the Company in this analysis include an estimate of the carrying costs during the expected lease-up periods considering current market conditions and costs to execute similar leases. In estimating carrying costs, the Company includes real estate taxes, insurance and other operating expenses and estimates of lost rents at market rates during the expected lease-up periods, which primarily range from four to twelve months. The Company also considers information obtained about each property as a result of its pre-acquisition due diligence, marketing and leasing activities in estimating the fair value of the tangible and intangible assets acquired. The Company also uses the information obtained as a result of its pre-acquisition due diligence as part of its consideration of the accounting standard governing asset retirement obligations and when necessary, will record a conditional asset retirement obligation as part of its purchase price. The Company also evaluates tenant relationships on a tenant-specific basis. On most of the Company’s acquisitions, this intangible has been deemed immaterial, in which case no related intangible asset value is assigned. In the event that a tenant terminates its lease, the unamortized portion of each intangible, including in-place lease values and tenant relationship values, is charged to expense and market rate adjustments (above or below) is recorded to revenue. The Company records development acquisitions that do not meet the accounting criteria to be accounted for as business combinations at the purchase price paid. Costs directly associated with development acquisitions accounted for as asset acquisitions are capitalized as part of the cost of the acquisition. Depreciation and Amortization The costs of buildings and improvements are depreciated using the straight-line method based on the following useful lives: buildings and improvements (5 to 55 years) and tenant improvements (the shorter of (i) the life of the asset, 1 to 16 years, or (ii) the lease term). Construction-in-Progress Project costs directly associated with the development and construction of a real estate project are capitalized as construction-in-progress. Construction-in-progress also includes costs related to ongoing tenant improvement projects. In addition, interest, real estate taxes and other expenses that are directly associated with the Company’s development activities are capitalized until the property is placed in service. Interest expense is capitalized using the Company’s weighted average interest rate. Internal direct costs are capitalized to projects in which qualifying expenditures are being incurred. Internal direct construction costs totaling $7.0 million in 2018, $6.1 million in 2017, $6.7 million in 2016 and interest totaling $3.6 million in 2018, $3.1 million in 2017, and $10.9 million in 2016 were capitalized related to the development of certain properties and land holdings. During the years ended December 31, 2018, 2017 and 2016, the Company’s internal direct construction costs are comprised entirely of capitalized salaries. The following table shows the amount of compensation costs (including bonuses and benefits) capitalized for the years presented (in thousands): December 31, 2018 2017 2016 Development $ 3,185 $ 4,390 $ 3,182 Redevelopment 968 319 144 Tenant Improvements 2,811 1,354 3,391 Total $ 6,964 $ 6,063 $ 6,717 Impairment or Disposal of Long-Lived Assets The Company reviews its long-lived assets for impairment following the end of each quarter using cash flow projections and estimated fair values for each of its properties where events or changes in circumstances indicate that the carrying amounts may not be recoverable. The Company updates leasing and other assumptions regularly, paying particular attention to properties where there is an event or change in circumstances that indicates an impairment in value. Additionally, the Company considers strategic decisions regarding the future development plans for property under development and other market factors. For long-lived assets to be held and used, the Company analyzes recoverability based on the estimated undiscounted future cash flows expected to be generated from the operations and eventual disposition of the assets over, in most cases, a 10-year hold period. If there is significant possibility that the Company will dispose of assets earlier, it analyzes the recoverability using a probability weighted analysis of the undiscounted future cash flows expected to be generated from the operations and eventual disposition of each asset using various probable hold periods. If the recovery analysis indicates that the carrying value of the tested property is not recoverable, the property is written down to its fair value and an impairment loss is recognized. In such case, an impairment loss is recognized in the amount of the excess of the carrying amount of the asset over its fair value. If and when the Company’s plans change, it revises its recoverability analysis to use cash flows expected from operations and eventual disposition of each asset using hold periods that are consistent with its revised plans. Estimated cash flows used in such analysis are based on the Company’s plans for the property and its views of market economic conditions. The estimates consider factors such as current and future rental rates, occupancies for the tested property and comparable properties, estimated operating and capital expenditures and recent sales data for comparable properties; most of these factors are derived from market data obtained from real estate leasing and brokerage firms and the Company’s direct experience with the properties and their markets. Assets Held for Sale The Company generally considers assets to be “held for sale” when the transaction has been approved by its Board of Trustees, or by officers vested with authority to approve the transaction, and there are no known significant contingencies relating to the sale of the property within one year of the consideration date and the consummation of the transaction is otherwise considered probable. When a property is designated as held for sale, the Company stops depreciating the property and estimates the property’s fair value, net of selling costs. If the determination is made that the estimated fair value, net of selling costs, is less than the net carrying value of the property, an impairment loss is recognized, reducing the net carrying value of the property to estimated fair value less selling costs. For periods in which a property is classified as held for sale, the Company classifies the assets and liabilities, as applicable, of the property as “held for sale” on the consolidated balance sheet for such periods. The relevant accounting guidance for impairments requires that qualifying assets and liabilities and the results of operations that have been sold, or otherwise qualify as “held for sale,” be presented as discontinued operations in all periods presented if the disposal represents a strategic shift that has, or will have, a major effect on the Company’s operations and financial results. The components of the property’s net income that is reflected as discontinued operations include the net gain (or loss) upon the disposition of the property held for sale, operating results, depreciation and interest expense (if the property is subject to a secured loan). Impairment of Land Held for Development When demand for build-to-suit office space declines and the ability to sell land held for development deteriorates, or other market factors indicate possible impairment in the recoverability of land held for development, it is reviewed for impairment by comparing its fair value to its carrying value. If the estimated sales value is less than the carrying value, the carrying value is written down to its estimated fair value. Cash and Cash Equivalents Cash and cash equivalents are highly-liquid investments with original maturities of three months or less. The Company maintains cash equivalents in money market accounts with financial institutions in excess of insured limits, but believes this risk is mitigated by only investing in or through major financial institutions. The Company does not invest its available cash balances in money market funds, as such available cash balances are appropriately reflected as cash and cash equivalents on the consolidated balance sheets. Restricted Cash Restricted cash consists of cash held as collateral to provide credit enhancement for the Company’s mortgage debt, cash for property taxes, capital expenditures and tenant improvements. Escrows also include cash held by qualified intermediaries for possible investments in like-kind exchanges in accordance with Section 1031 of the Internal Revenue Code in connection with sales of the Company’s properties. Restricted cash is included in the “Other assets” caption in the consolidated balance sheets. Accounts Receivable and Accrued Rent Receivable Generally, leases with tenants are accounted for as operating leases. Minimum lease payments under tenant leases are recognized on a straight-line basis over the term of the related lease. The cumulative difference between lease revenue recognized under the straight-line method and contractual lease payment terms are recorded as “Accrued rent receivable, net” on the consolidated balance sheets. Included in current tenant receivables are tenant reimbursements which are comprised of amounts recoverable from tenants for common area maintenance expenses and certain other recoverable expenses that are recognized as revenue in the period in which the related expenses are incurred. As of December 31, 2018 and 2017, no tenant represented more than 10% of accounts receivable and accrued rent receivable. Tenant receivables and accrued rent receivables are carried net of the allowances for doubtful accounts of $1.7 million and $11.3 million in 2018, respectively, and $3.5 million and $13.6 million in 2017, respectively. The tenant receivables allowance is an estimate based on two calculations that are combined to determine the total amount reserved. First, the Company evaluates specific accounts where it has determined that a tenant may have an inability to meet its financial obligations. In these situations, the Company uses its judgment, based on the facts and circumstances, and records a specific reserve for that tenant against amounts due to reduce the receivable to the amount that the Company expects to collect. These reserves are reevaluated and adjusted as additional information becomes available. Second, a reserve is established for all tenants based on a range of percentages applied to receivable aging categories for tenant receivables. For accrued rent receivables, the Company considers the results of the evaluation of specific accounts and also considers other factors including assigning risk factors to different industries based on its tenants Standard Industrial Classification (SIC). The accrued rent receivable allowance percentages are also based on historical collection and write-off experience adjusted for current market conditions, which requires management’s judgments. Investments in Unconsolidated Real Estate Ventures Under the equity method, investments in unconsolidated Real Estate Ventures are recorded initially at cost and subsequently adjusted for equity in earnings, contributions, distributions and impairments. For Real Estate Ventures that are constructing assets to commence planned principal operations, the Company capitalizes interest expense to the extent that it is recoverable using the Company’s weighted average interest rate of consolidated debt and its investment balance as a basis. Planned principal operations commence when a property is available to lease and at that point in time, the Company ceases capitalizing interest to its investment basis. During the twelve months ended December 31, 2018, the Company did not capitalize any interest expense. During the twelve months ended December 31, 2017 and 2016, the Company capitalized interest expense of $0.4 million and $1.9 million. On a periodic basis, management also assesses whether there are any indicators that the value of the Company’s investments in unconsolidated Real Estate Ventures may be other than temporarily impaired. An investment is impaired only if the value of the investment, as estimated by management, is less than the carrying value of the investment and the decline is other than temporary. To the extent that an impairment has occurred, the loss shall be measured as the excess of the carrying amount of the investment over the fair value of the investment, as estimated by management. Management is required to make significant judgements about the fair value of its ownership interests to determine if an impairment exists. Fair value is determined through various valuation techniques, including but not limited to, discounted cash flow models, quoted market values and third party appraisals. When the Company acquires an interest in or contributes assets to a real estate venture project, the difference between the Company’s cost basis in the investment and the value of the real estate venture or asset contributed is amortized over the life of the related assets, intangibles and liabilities and such adjustment is included in the Company’s share of equity in income of unconsolidated Real Estate Ventures. For purposes of cash flow presentation, distributions from unconsolidated Real Estate Ventures are presented as part of operating activities when they are considered as a return on investments. The Company elected, in connection with its adoption of ASU 2016-15, “Classification of Certain Cash Receipts and Cash Payments” (ASU 2016-15) during the fourth quarter of 2016, to continue to account for Deferred Costs Costs incurred in connection with property leasing are capitalized as deferred leasing costs. Deferred leasing costs consist primarily of leasing commissions and internal leasing costs that are amortized using the straight-line method over the life of the respective lease which generally ranges from 1 to 16 years. Management re-evaluates the remaining useful lives of leasing costs as economic and market conditions change. Notes Receivable The Company accounts for notes receivable on its balance sheet at amortized cost, net of allowance for loan losses. Interest income is recognized over the term of the notes receivable and is calculated based on the terms of the contractual terms of each note agreement. Notes receivable are placed on nonaccrual status when management determines, after considering economic and business conditions and collection efforts, that the loans are impaired or collection of interest is doubtful. Uncollectible interest previously accrued is recognized as bad debt expense. Interest income on nonaccrual loans is recognized only to the extent that cash payments are received. On June 26, 2018, the Company provided a $44.4 million mortgage loan with a 4.0% stated interest rate and maturing on June 25, 2023, to Brandywine 1919 Ventures, an unconsolidated real estate venture in which the Company holds a 50% ownership interest, and recorded a note receivable of $44.4 million. Additionally, a note receivable was given to an unaffiliated third party during the third quarter of 2016 to facilitate its acquisition and development of an industrial facility located in Pennsauken, New Jersey. The Company evaluated its investments in the notes receivable under ASC 310, “Receivables” and determined that the loans were provided at market terms and the Company does not participate in the residual profits of the unaffiliated third parties. Accordingly, the investments, totaling $47.8 million as of December 31, 2018 and $3.5 million as of December 31, 2017, have been classified on the Company’s consolidated balance sheets as notes receivable within the “Other assets” caption on the accompanying consolidated balance sheets. Deferred Financing Costs Costs incurred in connection with debt financing are capitalized as a direct deduction from the carrying value of the debt, except for costs capitalized related to the Company’s revolving credit facility, which are capitalized within the “Deferred costs, net” caption on the accompanying consolidated balance sheets. Deferred financing costs are charged to interest expense over the terms of the related debt agreements. Deferred financing costs consist primarily of loan fees which are amortized over the related loan term on a basis that approximates the effective interest method. Deferred financing costs are accelerated, when debt is extinguished, as part of the “Interest expense-amortization of deferred financing costs” caption within the Company’s consolidated statements of operations. Original issue discounts are recognized as part of the gain or loss on extinguishment of debt, as appropriate. Revenue Recognition In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606). Under Topic 606, revenue is recognized when a customer obtains control of promised goods or services and is recognized at an amount that reflects the consideration expected to be received in exchange for such goods or services. In addition, Topic 606 requires disclosure of the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. The Company adopted Topic 606 in the first quarter of 2018 using the modified retrospective method. This adoption, which required the Company to evaluate incomplete contracts as of January 1, 2018, related to the Company’s point of sale revenue, management, leasing and development fee arrangements and other sundry income. The Company’s analysis of incomplete contracts resulted in no cumulative effect adjustment to the consolidated balance sheets and statements of operations presented in its consolidated financial statements. Results for reporting periods beginning after January 1, 2018 are presented under Topic 606. The new guidance provides a unified model to determine how revenue is recognized. To determine the proper amount of revenue to be recognized, the Company performs the following steps: (i) identify the contract with the customer, (ii) identify the performance obligations within the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations and (v) recognize revenue when (or as) a performance obligation is satisfied. The following is a summary of revenue earned by the Company’s reportable segments (see Note 17, “Segment Information,” Twelve-month period ended December 31, 2018 Philadelphia CBD Pennsylvania Suburbs Metropolitan Washington, D.C. Austin, Texas Other Corporate Total Base rent $ 164,369 $ 118,628 $ 80,858 $ 21,757 $ 8,400 $ (1,964 ) $ 392,048 Straight-line rent 11,867 2,851 (1,577 ) 116 201 (449 ) 13,009 Point of sale 23,528 258 1,062 521 230 - 25,599 Total rents 199,764 121,737 80,343 22,394 8,831 (2,413 ) 430,656 Tenant reimbursements 51,572 14,440 3,519 10,736 2,832 (474 ) 82,625 Termination fees 192 1,435 136 - - - 1,763 Third party management fees, labor reimbursement and leasing 855 25 5,793 5,455 4,951 5,478 22,557 Other income 4,334 642 517 80 143 1,028 6,744 Total revenue $ 256,717 $ 138,279 $ 90,308 $ 38,665 $ 16,757 $ 3,619 $ 544,345 (a) Corporate includes intercompany eliminations necessary to reconcile to consolidated Company totals. Rental Revenue The Company owns, operates and manages commercial real estate. The Company’s primary source of revenue is leases which fall under the scope of Leases (Topic 840). Rental revenue is recognized on a straight-line basis over the term of the leases from the later of the date of the commencement of the lease or the date of acquisition of the property subject to existing leases. The straight-line rent adjustment increased revenue by approximately $10.4 million in 2018, $24.9 million in 2017 and $26.3 million in 2016. Deferred rents on the balance sheet represent rental revenue received prior to their due dates and amounts paid by the tenant for certain improvements considered to be landlord assets that will remain as the Company’s property at the end of the tenant’s lease term. The amortization of the amounts paid by the tenant for such improvements is calculated on a straight-line basis over the term of the tenant’s lease and is a component of straight-line rental income and increased revenue by $1.8 million in 2018, $2.2 million in 2017 and $2.1 million in 2016. Lease incentives, which are included as reductions of rental revenue in the accompanying consolidated statements of operations, are recognized on a straight-line basis over the term of the lease. Lease incentives decreased revenue by $1.5 million in 2018, $1.8 million in 2017 and $2.0 million in 2016. In addition, the Company’s rental revenue is impacted by the Company’s determination of whether improvements to the properties, whether made by the Company or by the tenant, are landlord assets. The determination of whether an improvement is a landlord asset requires judgment. In making this judgment, the Company’s primary consideration is whether the improvement would be utilizable by another tenant upon move out of the improved space by the then-existing tenant. If the Company has funded an improvement that it determines not to be landlord assets, then it treats the cost of the improvement as a lease incentive. If the tenant has funded the improvement that the Company determines to be landlord assets, then the Company treats the costs of the improvement as deferred revenue and amortizes this cost into revenue over the lease term. For certain leases, the Company makes significant assumptions and judgments in determining the lease term, including assumptions when the lease provides the tenant with an early termination option. The lease term impacts the period over which the Company determines and records minimum rents and also impacts the period over which the Company amortizes lease-related costs. No tenant repr

Real Estate Investments

Real Estate Investments	12 Months Ended
	Dec. 31, 2018
Real Estate [Abstract]
REAL ESTATE INVESTMENTS	3. REAL ESTATE INVESTMENTS As of December 31, 2018 and 2017, the gross carrying value of the operating properties was as follows (in thousands): December 31, December 31, 2018 2017 Land $ 508,363 $ 492,197 Building and improvements 3,029,427 2,896,113 Tenant improvements 415,529 444,038 Total $ 3,953,319 $ 3,832,348 2018 Acquisitions On December 19, 2018, the Company acquired an office property containing 120,559 rentable square feet located at 4516 Seton Center Parkway in Austin, Texas, known as Quarry Lake II, for a gross purchase price of $39.5 million. The purchase of Quarry Lake II is an asset acquisition under ASU 2017-01. The Company capitalized $0.1 million of acquisition-related costs and funded the acquisition with a borrowing of $39.0 million from the Company’s unsecured credit facility. On December 11, 2018, the Company acquired from DRA Advisors (“DRA”), its 50% ownership interest in the G&I Austin Office LLC real estate venture (the “DRA Austin Venture”) for an aggregate purchase price of $535.1 million. The DRA Austin Venture owned twelve office properties (“the Austin Venture Portfolio”) containing an aggregate 1,570,123 square feet located in Austin, Texas. As a result of the acquisition, the Company acquired complete ownership of the Austin Portfolio. The aggregate purchase price includes the carrying amount of the Company’s investment in DRA Austin Venture of $14.6 million. At settlement, the Company assumed $115.5 million of mortgage debt and received a credit at settlement of $130.7 million for a note receivable provided to the DRA Austin Venture on November 1, 2018. This note receivable was used to repay one of DRA Austin Venture’s mortgage loans prior to the December 11, 2018 acquisition date. The Company also obtained working capital of $24.9 million. Subsequent to receiving cash proceeds of $28.3 million for its promoted interest in the DRA Austin Venture and recognizing a remeasurement gain of $103.8 million, reflected in the caption “Net gain on real estate venture transactions” in the consolidated statements of operations, the Company funded the acquisition with an aggregate cash payment of $117.3 million. Additionally, the assumed mortgage debt of $115.5 million was repaid at settlement. Both cash payments were funded through borrowings under the Company’s unsecured credit facility. The Company recognized a $28.3 million gain on its promoted interest in the DRA Austin Venture, reflected in the caption “Gain on promoted interest in unconsolidated real estate venture” in the consolidated statements of operations. The gain on promoted interest was based off of the returns earned over the duration of the DRA Austin Venture and the returns were determined based on operating results and real estate valuation of the venture. The Company accounted for the acquisition of the Austin Venture Portfolio as an asset acquisition, and as a result, a nominal amount of transaction costs were capitalized to the basis of the acquired properties. The Company previously accounted for its 50% non-controlling interest in the DRA Austin Venture under the equity method of accounting. As a result of the Company’s acquistion of DRA’s 50% ownership interest in the DRA Austin Venture, the Company obtained control of DRA Austin Venture and the Company’s existing investment balance was remeasured based on the fair value of the underlying properties acquired and the existing distribution provisions under the relevant partnership agreement, including the Company’s entitlement to a distribution on account of its promoted interest. On June 29, 2018, the Company acquired, through a 99-year ground lease, the leasehold interest in a one-acre land parcel, located at 3025 JFK Boulevard, in Philadelphia, Pennsylvania. The Company prepaid $15.0 million of ground lease rent and, in accordance with ASC 840, capitalized $0.3 million of costs related to entering the lease. Additionally, the ground lease required the Company to pay $5.6 million for a leasehold valuation credit, which can be applied to increase the density of the projects subject to the Schuylkill Yards Project master development agreement. Of this credit, $2.4 million will be applied to the development of 3001-3003 and 3025 JFK Boulevard if the Company constructs a minimum of 1.2 million square feet of floor area ratio (“FAR”) on these land parcels. The remaining credit of $3.2 million can be used for development in excess of 1.2 million FAR at 3001-3003 and 3025 JFK Boulevard or toward future ground lease takedowns at the Schuylkill Yards Development Site. This $3.2 million credit is reimbursed if the master development agreement is terminated by the landowner. Based on the Company’s evaluation under ASC 840, the ground lease is classified as an operating lease. The ground lease and credit are included in the “Prepaid leasehold interests in land held for development, net” and “Other assets” captions, respectively, in the consolidated balance sheets. ASC 840, the ground lease is classified as an operating lease and included in the “Prepaid leasehold interests in land held for development, net, ” caption in the consolidated balance sheets . On January 5, 2018, the Company acquired, from its then partner in each of the Four Tower Bridge real estate venture and the Seven Tower Bridge real estate venture, the partner’s 35% ownership interest in the Four Tower Bridge real estate venture in exchange for the Company's 20% ownership interest in the Seven Tower Bridge real estate venture. As a result of this non-monetary exchange, the Company acquired 100% of the Four Tower Bridge real estate venture, which owns an office property containing 86,021 square feet, in Conshohocken, Pennsylvania, encumbered with $9.7 million in debt. The Company previously accounted for its noncontrolling interest in Four Tower Bridge using the equity method. As a result of the exchange transaction, the Company obtained control of the Four Tower Bridge property. The Company’s acquisition of the 35% ownership interest in Four Tower Bridge from its former partner resulted in the consolidation of the property, which has been accounted for as an asset acquisition under ASU 2017-01. As such, the Company capitalized $0.1 million of acquisition-related costs and allocated the unencumbered acquisition value, consisting of the fair value of $23.6 million and the acquisition-related costs, to tangible and intangible assets and liabilities. The unencumbered acquisition value was determined under the comparative sales approach, which utilized observable transactions within the Conshohocken submarket. The Company utilized a number of sources in making estimates of fair value for purposes of allocating the acquisition values to tangible and intangible assets acquired. The acquisition values have been allocated as follows (in thousands): Quarry Lake II Austin Venture Portfolio Four Tower Bridge Acquisition Date 12/19/2018 12/11/2018 01/05/2018 Building, land and improvements $ 35,120 $ 457,390 $ 20,734 Intangible assets acquired 5,809 76,925 3,144 Below market lease liabilities assumed (1,524 ) (13,769 ) (182 ) Deferred gain (a) - 14,594 - Total unencumbered acquisition value $ 39,405 $ 535,140 $ 23,696 Mortgage debt assumed - at fair value (b) - - (9,940 ) Total encumbered acquisition value $ 39,405 $ 535,140 $ 13,756 Total unencumbered acquisition value 39,405 535,140 23,696 Mortgage debt assumed - at fair value (b) - - (9,940 ) Mortgage debt repaid at settlement (c) - (115,461 ) - Investment in unconsolidated real estate ventures - (14,594 ) (3,502 ) Gain on promoted interest in unconsolidated real estate venture - (28,283 ) - Gain on real estate venture transactions - (103,847 ) (11,633 ) Purchase price reduction for note receivable (d) - (130,742 ) - Net working capital assumed (368 ) (24,865 ) 1,379 Total cash payment at settlement $ 39,037 $ 117,348 $ - Weighted average amortization period of intangible assets - 5.5 years 4.1 years Weighted average amortization period of below market liabilities assumed 3.0 years 4.6 years 4.8 years (a) Represents a deferred gain resulting recognized at settlement, which resulted in a reduction in the acquisition value. (b) The outstanding principal balance on mortgage debt for Four Tower Bridge (c) On December 11, 2018, the Company assumed $115.5 million of mortgage debt which was repaid in full at settlement. (d) Represents a note receivable due from the DRA Austin Venture that represents a purchase price reduction. Quarry Lake II contributed approximately $0.1 million of revenue and $0.1 million of net income, included in the Company’s consolidated statements of operations, for the twelve-month period ended December 31, 2018. Austin Venture Portfolio contributed approximately $3.4 million of revenue and $1.3 million of net loss, included in the Company’s consolidated statements of operations, for the twelve-month period ended December 31, 2018. Four Tower Bridge contributed approximately $2.8 million of revenue and $0.3 million of net income, included in the Company’s consolidated statements of operations, for the twelve-month period ended December 31, 2018. The unaudited pro forma information below summarizes the Company’s combined results of operations for the years ended December 31, 2018 and December 31, 2017, respectively, as though the acquisition of the Austin Venture Portfolio was completed on January 1, 2017. The supplemental pro forma operating data is not necessarily indicative of what the actual results of operations would have been assuming the transaction had been completed as set forth above, nor do they purport to represent the Company’s results of operations for future periods (in thousands, except for per share amounts). December 31, 2018 2017 Pro forma revenue $ 602,713 $ 582,244 Pro forma net income 134,142 115,475 Pro forma net income available to common shareholders 134,142 115,475 Dispositions The Company sold the following properties during the twelve-month period ended December 31, 2018 (dollars in thousands): Disposition Date Property/Portfolio Name Location Type Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) December Subaru Camden, NJ Mixed-use 1 83,000 $ 45,300 $ 44,877 $ 2,570 December Rockpoint Herndon, VA Office 8 1,293,197 312,000 262,442 397 June 20 Gibbsboro, NJ Office 1 38,260 2,000 1,850 (35 ) Total 10 1,414,457 $ 359,300 $ 309,169 $ 2,932 (a) During the second quarter of 2018, Subaru exercised its purchase option under the lease agreement for the Subaru NSTC and the sale occurred during the fourth quarter of 2018. See Note 2, “ Summary of Significant Accounting Policies ,” for further discussion of the lease agreement and related revenue recognition. (b) On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment (the “Rockpoint Portfolio”) to a newly-formed joint venture (the “Herndon Innovation Center Metro Portfolio Venture, LLC”) for a gross sales price of $312.0 million. The Company and its partner own 15% and 85% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. The Herndon Innovation Center Metro Portfolio Venture, LLC funded the acquisition with $265.2 million of cash, which was distributed to the Company at closing. After funding its share of closing costs and working capital contributions of $2.2 million and $0.6 million, respectively, the Company received $262.4 million of cash proceeds at settlement. The Company recorded an impairment charge of $56.9 million for the Rockpoint Portfolio during the third quarter of 2018. The Company recorded a $0.4 million gain on sale, which represents an adjustment to estimated closing costs used to determine the impairment charge in the third quarter of 2018. For further information related to this transaction, see the “ Herndon Innovation Center Metro Portfolio Venture, LLC Investment in Unconsolidated Real Estate Ventures The Company sold the following land parcels during the twelve-month period ended December 31, 2018 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale March 16, 2018 Garza Ranch - Office Austin, TX 1 6.6 $ 14,571 $ 14,509 $ 1,515 (a) January 10, 2018 Westpark Land Durham, NC 1 13.1 485 412 22 Total Dispositions 2 19.7 $ 15,056 $ 14,921 $ 1,537 (a) As of March 31, 2018, the Company had not transferred control to the buyer of this land parcel, or two other parcels at this site which were sold during 2017, because of a completion guarantee which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The cash received at settlement was recorded as “Deferred income, gains and rent” on the Company’s consolidated balance sheets. During the three months ended June 30, 2018, the infrastructure improvements were substantially completed, at which time the Company transferred control of the land parcels. As a result, the Company then recognized the sales of the three land parcels during 2018 and recorded an aggregate $2.8 million gain. During the quarter ended December 31, 2018, the Company recognized an additional $0.2 million gain. See Note 2, “Summary of Significant Accounting Policies,” The sales of property and land referenced above do not represent a strategic shift that has a major effect on the Company’s operations and financial results. Accordingly, the operating results of these properties remain classified within continuing operations for all periods presented. Held for Use Impairment As of December 31, 2018, the Company evaluated the recoverability of the carrying values of certain properties that triggered an assessment under the undiscounted cash flow model. Based on its evaluation, the Company determined it would not recover the carrying value of one property in its Other segment, 1900 Gallows Road, located in Vienna, Virginia, due to a reduction in the intended hold period. Accordingly, the Company recorded an impairment charge of $14.8 million at December 31, 2018, reflected in the results for the twelve-month period ended December 31, 2018, which reduced the carrying value of the property from $52.8 million to its estimated fair value of $38.0 million. The Company measured this impairment based on a discounted cash flow analysis, using a hold period of ten years and a residual capitalization rate and discount rate of 7.5% and 9.5%, respectively. The result was comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” Held for Sale The following is a summary of properties classified as held for sale but which did not meet the criteria to be classified within discontinued operations at December 31, 2018 (in thousands): Held for Sale Properties December 31, 2018 Pennsylvania Suburbs - Land (a) Other - Land (a) Total ASSETS HELD FOR SALE Real estate investments: Land inventory $ 4,254 $ 7,345 $ 11,599 Total real estate investments 4,254 7,345 11,599 Total assets held for sale, net $ 4,254 $ 7,345 $ 11,599 (a) As of December 31, 2018, the Company determined that the sales of one land parcel in its Pennsylvania Suburbs segment and two parcels of land in its Other segment were probable and classified these properties as held for sale in accordance with applicable accounting standards for long-lived assets. At such date, the fair value less the anticipated costs of sale of the properties exceeded the carrying values. As a result, there is no impairment. The fair value measurement will be based on the pricing in the purchase and sale agreements The disposals of the properties referenced above do not represent a strategic shift that has a major effect on the operations and financial results of the Company. As a result, the operating results of the properties remain classified within continuing operations for all periods presented. Held for Sale Impairment As of September 30, 2018, the Company determined that the sale of eight office properties, known as the Rockpoint Portfolio, containing 1,293,197 rentable square feet, in the Metropolitan Washington, D.C. segment, was probable and classified these properties as held for sale in accordance with applicable accounting standards for long-lived assets. At such date, the $366.0 million carrying value of the properties exceeded the estimated $309.1 million fair value less the anticipated costs of sale. As a result, the Company recognized an impairment loss totaling approximately $56.9 million during the three-month period ended September 30, 2018. The Company measured this impairment based on a discounted cash flow analysis, using a hold period of ten years and residual capitalization rates and discount rates of 7.47% and 8.60%, respectively. The results were comparable to indicative pricing in the market. As significant inputs to the model are unobservable, the Company determined that the value determined for this property falls within Level 3 fair value reporting. The Rockpoint Portfolio was sold during the fourth quarter of 2018. See the “Dispositions” 2017 Acquisitions On October 13, 2017, the Company acquired, through a 99-year prepaid ground lease, the leasehold interest in an office property containing 282,709 rentable square feet located at 3025 Market Street in Philadelphia, Pennsylvania, known as The Bulletin Building, for a gross purchase price of $35.0 million. The purchase of The Bulletin Building is an asset acquisition under ASU 2017-01. The Company utilized a number of sources in making estimates of fair value for purposes of allocating the purchase price to tangible and intangibles assets acquired. October 13, 2017 Building and improvements $ 30,583 Construction-in-progress 672 Intangible assets acquired (a) 10,575 Below market lease liabilities assumed (b) (4,055 ) $ 37,775 (a) Weighted average amortization period of 7.9 years. (b) Weighted average amortization period of 7.0 years. The Bulletin Building contributed approximately $1.2 million of revenue and approximately $0.4 million of net loss in the Company’s consolidated statements of operations, for the period from October 13, 2017 through December 31, 2017. On July 28, 2017, the Company acquired an office building containing 58,587 rentable square feet located at 3000 Market Street, in Philadelphia, Pennsylvania, for $32.7 million. The acquisition was the Section 1031 exchange receiver for the sale of Concord Airport Plaza. See property disposition table below. The purchase of 3000 Market Street is an asset acquisition under ASU 2017-01. As such, the Company capitalized $0.7 million of acquisition-related costs and allocated the purchase price, consisting of the contractual purchase price of $32.0 million and the acquisition related costs, to the tangible and intangible assets. The Company utilized a number of sources in making estimates of fair value for purposes of allocating the purchase price to tangible and intangibles assets acquired. The purchase price has been allocated as follows (in thousands): July 28, 2017 Building, land and improvements $ 32,004 Intangible assets acquired (a) 2,562 Below market lease liabilities assumed (b) (1,818 ) $ 32,748 (a) Weighted average amortization period of 5.9 years. (b) Weighted average amortization period of 6.0 years. 3000 Market Street contributed approximately $0.8 million of revenue and a $0.5 million of net loss in the Company’s consolidated statements of operations, for the period from July 28, 2017 through December 31, 2017. Dispositions The Company sold the following properties during the twelve-month period ended December 31, 2017 (dollars in thousands): Disposition Date Property/Portfolio Name Location Type Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) on Sale (a) November 22, 2017 11, 14, 15, 17 and 18 Campus Boulevard (Newtown Square) Newtown Square, PA Office 5 252,802 $ 42,000 $ 40,459 $ 19,642 October 31, 2017 630 Allendale Road King of Prussia, PA Office 1 150,000 17,500 16,580 3,605 June 27, 2017 Two, Four A, Four B and Five Eves Drive (Evesham Corporate Center) Marlton, NJ Office 4 134,794 9,700 8,650 (325 ) (b) June 12, 2017 7000 Midlantic Drive Mount Laurel, NJ Retail 1 10,784 8,200 7,714 1,413 March 30, 2017 200, 210 & 220 Lake Drive East (Woodland Falls) Cherry Hill, NJ Office 3 215,465 19,000 17,771 (249 ) (c) March 15, 2017 Philadelphia Marine Center (Marine Piers) Philadelphia, PA Mixed-use 1 181,900 21,400 11,182 6,498 (d) March 13, 2017 11700, 11710, 11720 & 11740 Beltsville Drive (Calverton) Beltsville, MD Office 3 313,810 9,000 8,354 - (e) February 2, 2017 1200 & 1220 Concord Avenue (Concord Airport Plaza) Concord, CA Office 2 350,256 33,100 32,010 551 (f) Total Dispositions 20 1,609,811 $ 159,900 $ 142,720 $ 31,135 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) As of March 31, 2017, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of four properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $1.0 million at March 31, 2017, which reduced the aggregate carrying values of the properties from $10.2 million to their estimated fair value of $9.2 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.00% and 9.25%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs. (c) As of December 31, 2016, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of three properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $7.3 million at December 31, 2016, reducing the aggregate carrying values of the properties from $25.8 million to their estimated fair value of $18.5 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 8.75% and 9.00%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs (d) On March 15, 2017, the Company sold its sublease interest in the Piers at Penn’s Landing (the “Marine Piers”), which includes leasehold improvements containing 181,900 net rentable square feet, and a marina, located in Philadelphia, Pennsylvania for an aggregate sales price of $21.4 million. On the closing date, the buyer paid $12.0 million in cash. The $9.4 million balance of the purchase is due on (a) January 31, 2020, in the event that the tenant at the Marine Piers does not exercise an option it holds to extend the term of the sublease or (b) January 15, 2024, in the event that the tenant does exercise the option to extend the term of the sublease. The Company determined that it is appropriate to account for the sales transaction under the cost recovery method. The Company received cash proceeds of $11.2 million, after closing costs and prorations, and the net book value of the Marine Piers was $4.7 million, resulting in a gain on sale of $6.5 million. The remaining gain on sale of $9.4 million will be recognized on the second purchase price installment date. Prior to its sale, the Marine Piers had been classified as mixed-use within the Company’s property count (e) During the fourth quarter of 2016, the Company recognized a $3.0 million impairment related to these properties. During the first quarter of 2017, there was a price reduction of $1.7 million under the agreement of sale and an additional impairment of $1.7 million was recognized (f) During the fourth quarter of 2016, the Company recognized an $11.5 million impairment related to these properties. This sale was designated as a like-kind exchange under Section 1031 of the Internal Revenue Code (“IRC”) and, as such, the proceeds, totaling $32.0 million after closing costs and prorations, were deposited with a Qualified Intermediary, as defined under the IRC. The proceeds received at closing were recorded as “Other assets” in the Company’s consolidated balance sheets. During the third quarter of 2017, the Company acquired 3000 Market Street in Philadelphia, Pennsylvania using the full balance of the Section 1031 proceeds. See “ Acquisition In addition to the amounts in the table above, the Company recorded a $0.5 million gain during the first quarter of 2017 from the receipt of additional proceeds from the disposition of Cira Square in 2016. For further information relating to this sale, see the dispositions table in the 2016 section below. The Company sold the following land parcels during the twelve-month period ended December 31, 2017 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale September 13, 2017 50 E. Swedesford Square Malvern, PA 1 12.0 $ 7,200 $ 7,098 $ 882 July 18, 2017 Bishop's Gate Mount Laurel, NJ 1 49.5 6,000 5,640 71 (a) April 28, 2017 Garza Ranch - Multi-family Austin, TX 1 8.4 11,800 11,560 - (b) February 15, 2017 Gateway Land - Site C Richmond, VA 1 4.8 1,100 1,043 - (c) January 30, 2017 Garza Ranch - Hotel Austin, TX 1 1.7 3,500 3,277 - (b) Total Dispositions 5 76.4 $ 29,600 $ 28,618 $ 953 (a) During the fourth quarter of 2016, the Company recognized an impairment of $3.0 million. During the second quarter of 2017, the Company recorded a held for sale impairment charge of $0.3 million, reducing the aggregate carrying value of the land parcel from $5.9 million to its estimated fair value less costs to sell of $5.6 million. The fair value measurement is based on pricing in the purchase and sale agreement for the property. As the pricing in the purchase and sale agreement is unobservable, the Company determined that the input utilized to determine fair value for the property falls within Level 3 in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The land parcel was sold on July 18, 2017. (b) The Company has a continuing involvement in this property through a completion guaranty, which requires the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The Company recorded the cash received at settlement as “Deferred income, gains and rent” on the Company’s consolidated balance sheet and the Company will recognize the sale upon completion of infrastructure improvements. (c) During the fourth quarter of 2016, the Company recognized a nominal impairment related to this land parcel. The sales of properties, land and the land parcel held for sale do not represent a strategic shift that has a major effect on the Company's operations and financial results. Accordingly, the operating results of these properties remain classified within continuing operations for all periods presented. Held for Use Impairment As of December 31, 2017, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment. Based on the analysis, no impairment charges were identified during the three-month period ended December 31, 2017. As of March 31, 2017, the Company evaluated the recoverability of the carrying value of its properties that triggered an assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of four properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $1.0 million at March 31, 2017, reflected in the results for the twelve-month period ended December 31, 2017, reducing the aggregate carrying values of the properties from $10.2 million to their estimated fair value of $9.2 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.00% and 9.25%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” Land Impairment As of December 31, 2017, the Company evaluated the recoverability of the carrying value of its land parcels that triggered assessment. Based on the analysis, no impairment charges were identified during the three-month period ended December 31, 2017. See above land disposition table for detail of the Bishop’s Gate land parcel, on which a $0.3 million impairment charge was recorded as of June 30, 2017. Held for Sale As of December 31, 2017, the Company had land held for development, consisting of a 13.1-acre parcel of land located in the Company’s Other segment, classified as held for sale but which did not meet the criteria to be classified within discontinued operations. Accordingly, as of December 31, 2017, $0.4 million was reclassified from ‘Land held for development’ to ‘Assets held for sale, net’ on the consolidated balance sheets. There were no other reclassifications related to this parcel of land. As of December 31, 2017, the carrying value of the land was less than the fair value less the anticipated costs of sale and, as such, the Company expects to record a nominal gain on sale. The fair value measurement is based on the pricing in the purchase and sale agreement. The sale of the Company’s fee interest in the property referenced above does not represent a strategic shift that has a major effect on the Company's operations and financial results. As a result, the operating results of this property remains classified within continuing operations for all periods presented. 2016 Acquisition On July 1, 2016, the Company acquired 34.6 acres of land located in Austin, Texas known as the Garza Ranch for a gross purchase price of $20.6 million. The Company accounted for this transaction as an asset acquisition and capitalized approximately $1.9 million of acquisition related costs and closing costs as part of land held for development on its consolidated balance sheet. The Company funded the acquisition with $20.4 million of available corporate funds, net of prorations and other adjustments. As of December 31, 2017, the Company sold 9.5 acres (of the 34.6 acres) to two unaffiliated third parties. As of December 31, 2016, the land under this agreement of sale did not meet the criteria to be classified as held for sale. The Company had a continuing involvement through a completion guaranty, which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. See “ 2017 ” section above for information related to the sale of 1.7 acres. Dispositions The Company sold the following properties during the twelve-month period ended December 31, 2016 (dollars in thousands): Disposition Date Property/Portfolio Name Location Numbe

Investment in Unconsolidated Re

Investment in Unconsolidated Real Estate Ventures	12 Months Ended
	Dec. 31, 2018
Equity Method Investments And Joint Ventures [Abstract]
INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES	4. INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES As of December 31, 2018, the Company held ownership interests in ten unconsolidated Real Estate Ventures for an aggregate investment balance of $169.1 million. The Company formed or acquired interests in these Real Estate Ventures with unaffiliated third parties to develop or manage office, residential and/or mixed-use properties or to acquire land in anticipation of possible development of office, residential and/or mixed-use properties. As of December 31, 2018, six of the real estate ventures owned properties that contained an aggregate of approximately 5.8 million net rentable square feet of office space; two real estate ventures owned 1.4 acres of land held for development; one real estate venture owned 1.3 acres of land in active development; and one real estate venture owned a residential tower that contains 321 apartment units. The Company accounts for its unconsolidated interests in the Real Estate Ventures using the equity method. The Company’s unconsolidated interests range from 15% to 70%, subject to specified priority allocations of distributable cash in certain of the Real Estate Ventures. The Company earned management fees from its Real Estate Ventures of $6.3 million, $6.4 million and $6.7 million for the years ended December 31, 2018, 2017 and 2016, respectively. The Company earned leasing commission income from its Real Estate Ventures of $2.5 million, $4.5 million and $3.8 million for the years ended December 31, 2018, 2017 and 2016, respectively. The Company has outstanding accounts receivable balances from its Real Estate Ventures of $0.8 million and $0.9 million for the years ended December 31, 2018 and 2017, respectively. The amounts reflected in the following tables (except for the Company’s share of equity and income) are based on the historical financial information of the individual Real Estate Ventures. The Company does not record operating losses of a Real Estate Venture in excess of its investment balance unless the Company is liable for the obligations of the Real Estate Venture or is otherwise committed to provide financial support to the Real Estate Venture. The Company’s investment in Real Estate Ventures as of December 31, 2018 and 2017, and the Company’s share of the Real Estate Ventures’ income (loss) for the years ended December 31, 2018 and 2017 was as follows (in thousands): Ownership Carrying Amount Company's Share of Real Estate Venture Income (Loss) Real Estate Venture Debt at 100% Current Interest Debt Percentage (a) 2018 2017 2018 2017 2018 2017 Rate Maturity Office Properties Brandywine-AI Venture LLC (b) 50% $ 11,731 $ 43,560 $ (14,559 ) $ (4,465 ) $ 26,111 $ 93,117 4.65% (c) Rockpoint Venture (d) 15% 47,834 - 83 - - - MAP Venture (e) 50% 11,173 15,450 (2,155 ) (3,443 ) 185,000 180,800 L+2.45% Aug 2023 (e) PJP VII 25% 1,100 1,156 157 175 3,777 4,792 L+2.65% Dec 2019 PJP II 30% 663 604 179 72 2,214 2,564 6.12% Nov 2023 PJP VI 25% 125 179 71 38 7,069 7,370 6.08% Apr 2023 DRA (G&I) Austin (f) 50% - 13,972 1,687 (989 ) - 249,481 Four Tower Bridge (g) 65% - 3,032 - 746 - 9,749 Other Brandywine 1919 Ventures (h) 50% 19,897 22,268 253 (194 ) 88,860 88,860 4% Jun 2023 (i) HSRE-BDN I, LLC 50% - 17,671 (358 ) 449 - 110,886 TB-BDN Plymouth Apartments (j) - - - 99 - - Development Properties 4040 Wilson (k) 50% 37,371 37,179 (192 ) (255 ) 57,288 6,664 L+2.75% Dec 2021 51 N Street 70% 21,368 21,212 (137 ) (176 ) - - 1250 First Street Office 70% 17,838 17,867 (260 ) (149 ) - - Seven Tower Bridge (g) 20% - 471 - (214 ) - 14,629 $ 169,100 $ 194,621 $ (15,231 ) $ (8,306 ) $ 370,319 $ 768,912 (a) Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable. (b) See “ Brandywine - AI Venture: Station Square and 7101 Wisconsin Avenu e” and “ Brandywine - AI Venture: Other Than Temporary Impairment” sections below for information discussing activity that occurred during 2018 and 2017 relating to this venture. (c) The debt for these properties is comprised of one fixed rate mortgage: (1) $26.1 million with a 4.65% fixed interest rate due January 1, 2022. On December 28, 2018, the BDN – (d) On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment, known as the Rockpoint Portfolio, to a newly-formed joint venture, known as the Herndon Innovation Center Metro Portfolio Venture, LLC, for a gross sales price of $312.0 million. Rockpoint and the Company own 85% and 15% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. See “ Herndon Innovation Center Metro Portfolio Venture, LLC ” section below for further details. (e) On August 1, 2018, the MAP Venture refinanced its $180.8 million third party debt financing, secured by the buildings of MAP Venture and maturing February 9, 2019, with $185.0 million third party debt financing, also secured by the buildings, bearing interest at LIBOR + 2.45% capped at a total maximum interest of 6.00% and maturing on August 1, 2023. (f) See “ Austin Venture ” section below for information discussing the Company’s purchase of its partner’s entire 50 % interest in the twelve remaining properties within the Austin Venture on December 11, 2018. (g) On January 5, 2018, the Company exchanged its 20% interest in Seven Tower Bridge to acquire the remaining 35% interest in Four Tower Bridge. For further information regarding the accounting of the transaction, see “ Four Tower Bridge Acquisition (h) The basis difference associated with this venture is allocated between cost and the underlying equity in the net assets of the investee and is accounted for as if the entity were consolidated (i.e., allocated to the Company’s relative share of assets and liabilities with an adjustment to recognize equity in earnings for the appropriate depreciation/amortization). (i) On June 26, 2018, each of the Company and its partner, LCOR/Calstrs, provided a $44.4 million mortgage loan to Brandywine 1919 Ventures. As a result, the Company recorded a related-party note receivable of $44.4 million in the “Other assets” caption on its consolidated balance sheets. The loans bear interest at a fixed 4.0% per annum interest rate with a scheduled maturity on June 25, 2023. On June 26, 2018, Brandywine 1919 Ventures used the loan to repay the venture’s then outstanding $88.8 million construction loan, comprised of $88.6 million in principal and $0.2 million of accrued interest. (j) On January 31, 2017, the Company sold its 50% interest in TB-BDN Plymouth Apartments, LP. (k) During the fourth quarter of 2017, 4040 Wilson obtained a secured construction loan with a total borrowing capacity of $150.0 million. The following is a summary of the financial position of the Real Estate Ventures as of December 31, 2018 and December 31, 2017 (in thousands): December 31, 2018 DRA Brandywine-AI evo Other Total Net property $ - $ 47,043 $ - $ 788,940 $ 835,983 Other assets - 11,206 - 148,293 159,499 Other liabilities - 2,002 - 83,679 85,681 Debt, net - 26,020 - 339,687 365,707 Equity (c) - 30,227 - 513,867 544,094 December 31, 2017 DRA Brandywine-AI evo Other Total Net property $ 263,557 $ 158,960 $ 143,990 $ 517,458 $ 1,083,965 Other assets 42,272 24,181 8,563 86,916 161,932 Other liabilities 24,131 4,493 1,648 67,435 97,707 Debt, net 248,700 92,917 110,136 314,667 766,420 Equity (c) 32,998 85,731 40,769 222,272 381,770 (a) On December 11, 2018, the Company acquired DRA’s 50% ownership interest in the DRA Austin Venture for an aggregate purchase price of $535.1 million. See “Austin Venture” (b) On January 10, 2018, HSRE-BDN I, LLC (evo at Cira Centre South) sold the 345-unit student housing tower, its sole operating asset. See “ evo at Cira Disposition (c) 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. The following is a summary of results of operations of the Real Estate Ventures in which the Company had interests as of December 31, 2018 , 2017 and 2016 (in thousands): Twelve-month period ended December 31, 2018 DRA Brandywine-AI evo Other Total Revenue $ 53,476 $ 23,515 $ 163 $ 88,172 $ 165,326 Operating expenses (22,994 ) (10,483 ) (256 ) (48,302 ) (82,035 ) Interest expense, net (9,083 ) (3,478 ) (123 ) (17,090 ) (29,774 ) Depreciation and amortization (19,226 ) (8,991 ) (409 ) (25,200 ) (53,826 ) Provision for impairment - (20,832 ) - - (20,832 ) Loss on extinguishment of debt (356 ) (695 ) - (334 ) (1,385 ) Net income (loss) $ 1,817 $ (20,964 ) $ (625 ) $ (2,754 ) $ (22,526 ) Ownership interest % 50 % 50 % 50 % (a) Company's share of net income (loss) $ 909 $ (10,482 ) $ (313 ) $ (2,038 ) $ (11,924 ) Other-than-temporary impairment (b) - (4,076 ) - - (4,076 ) Basis adjustments and other 778 (1 ) (45 ) 37 769 Equity in income (loss) of Real Estate Ventures $ 1,687 $ (14,559 ) $ (358 ) $ (2,001 ) $ (15,231 ) Twelve-month period ended December 31, 2017 DRA Brandywine-AI evo Other Total Revenue $ 85,500 $ 29,500 $ 12,285 $ 88,986 $ 216,271 Operating expenses (35,997 ) (12,298 ) (3,075 ) (47,970 ) (99,340 ) Interest expense, net (13,985 ) (4,707 ) (4,092 ) (17,429 ) (40,213 ) Depreciation and amortization (34,026 ) (11,428 ) (4,512 ) (28,474 ) (78,440 ) Loss on extinguishment of debt (2,613 ) (811 ) - - (3,424 ) Net income (loss) $ (1,121 ) $ 256 $ 606 $ (4,887 ) $ (5,146 ) Ownership interest % 50 % 50 % 50 % (a) Company's share of net income (loss) $ (560 ) $ 128 $ 303 $ (1,735 ) $ (1,864 ) Other-than-temporary impairment (b) - (4,844 ) - - (4,844 ) Basis adjustments and other (429 ) 251 146 (1,566 ) (1,598 ) Equity in income (loss) of Real Estate Ventures $ (989 ) $ (4,465 ) $ 449 $ (3,301 ) $ (8,306 ) Twelve-month period ended December 31, 2016 DRA Brandywine-AI evo Other Total Revenue $ 85,749 $ 31,047 $ 12,393 $ 85,263 $ 214,452 Operating expenses (37,643 ) (13,654 ) (3,183 ) (48,712 ) (103,192 ) Provision for impairment (c) - (10,476 ) - - (10,476 ) Interest expense, net (15,052 ) (5,825 ) (3,230 ) (16,207 ) (40,314 ) Depreciation and amortization (38,365 ) (12,811 ) (4,512 ) (30,050 ) (85,738 ) Net income (loss) (d) $ (5,311 ) $ (11,719 ) $ 1,468 $ (9,706 ) $ (25,268 ) Ownership interest % 50 % 50 % 50 % (a) Company's share of net income (loss) $ (2,656 ) $ (5,860 ) $ 734 $ (4,719 ) $ (12,501 ) Basis adjustments and other 776 (35 ) 109 148 998 Equity in income (loss) of Real Estate Ventures $ (1,880 ) $ (5,895 ) $ 843 $ (4,571 ) $ (11,503 ) (a) See above table, which discloses the Company’s investment in Real Estate Ventures as of December 31, 2018 and 2017, for the Company’s unconsolidated ownership interests, subject to specified priority allocations of distributable cash, in certain of the Real Estate Ventures. (b) See “ Brandywine - AI Venture: Other Than Temporary Impairment” section below (c) See “ Brandywine - AI Venture: Station Square Impairment” (d) During the year ended December 31, 2016, there were $7.1 million of acquisition deal costs related to the formation of the MAP Venture. As of December 31, 2018, the aggregate principal payments of recourse and non-recourse debt payable to third-parties are as follows (in thousands): 2019 $ 4,998 2020 1,290 2021 58,651 2022 25,277 2023 280,005 Thereafter 98 Total principal payments 370,319 Net deferred financing costs (4,612 ) Outstanding indebtedness $ 365,707 Herndon Innovation Center Metro Portfolio Venture, LLC On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment, to a newly-formed joint venture, known as the Herndon Innovation Center Metro Portfolio Venture, LLC (“Herndon Innovation Center”), for a gross sales price of $312.0 million. The Company and its partner own 15% and 85% interests in the Herndon Innovation Center, respectively. The Herndon Innovation Center funded the acquisition with $265.2 million of cash, which was distributed to the Company at closing. After funding its share of closing costs and working capital contributions of $2.2 million and $0.6 million, respectively, the Company received $262.4 million of cash proceeds at settlement and was given a $47.7 million capital credit for its share of the fair value of the Herndon Innovation Center. The Company recorded an impairment charge of $56.9 million for the Herndon Innovation Center during the third quarter of 2018. The Company recorded a $0.4 million gain on sale, which represents an adjustment to estimated closing costs used to determine the impairment charge in the third quarter of 2018. As part of the transaction, the Company’s subsidiary management company executed an agreement with the Herndon Innovation Center to provide property management and leasing services to the Herndon Innovation Center. Based on the facts and circumstances at the formation of the Herndon Innovation Center, the Company determined that the venture is not a VIE in accordance with the accounting standard for the consolidation of VIEs. As a result, the Company used the voting interest model under the accounting standard for consolidation in order to determine whether to consolidate the Herndon Innovation Center. Based upon each member's substantive participating rights over the activities of the Herndon Innovation Center under the operating and related agreements of the Herndon Innovation Center, it is not consolidated by the Company, and is accounted for under the equity method of accounting. As a result, the Company measured its equity interest at fair value based on the fair value of the Herndon Innovation Center properties and the distribution provisions of the real estate venture agreement. Since the Company retains a non-controlling interest in the Herndon Innovation Center and there are no other facts and circumstances that preclude the consummation of a sale, the contribution qualifies as a sale of a nonfinancial asset under the relevant guidance. Austin Venture On October 16, 2013, the Company contributed a portfolio of seven office properties containing an aggregate of 1,398,826 rentable square feet located in Austin, Texas (the “Austin Properties”) to a newly-formed joint venture (the “Austin Venture”) with G&I VII Austin Office LLC (“DRA”). DRA and the Company agreed to an aggregate gross sales price of $330.0 million subject to an obligation on the Company’s part to fund the first $5.2 million of post-closing capital expenditures, of which $0.8 million was funded by the Company during 2013 and the remaining $4.4 million was funded by the Company during the twelve months ended December 31, 2014. DRA owned a 50% interest in the Austin Venture and the Company owned a 50% interest in the Austin Venture, subject to the Company’s right to receive up to an additional 10% of distributions. At closing the Austin Venture incurred third party debt financing of approximately $230.6 million secured by mortgages on the Austin Properties and used proceeds of this financing together with $49.7 million of cash contributions by DRA (less $1.9 million of closing costs and $6.9 million of closing prorations and lender holdbacks) to fund a $271.5 million distribution to the Company. The Company agreed to fund the first $5.2 million of post-closing capital expenditures on behalf of the Austin Venture, resulting in net proceeds of $266.3 million after funding the Company’s capital expenditure obligation. As part of the transaction, the Company’s subsidiary management company executed an agreement with the Austin Venture to provide property management and leasing services to the Austin Venture in exchange for a market-based fee. The Company measured its equity interest at fair value based on the fair value of the Austin Properties and the distribution provisions of the real estate venture agreement. Since the Company retained a noncontrolling interest in the Austin Properties and there were no other facts and circumstances that precluded the consummation of a sale, the contribution qualified as a partial sale of real estate under the relevant guidance for sales of real estate. On April 3, 2014, the Company contributed two three-story, Class A office buildings, commonly known as “Four Points Centre,” containing an aggregate of 192,396 net rentable square feet in Austin, Texas to the Austin Venture. On July 31, 2014, the Austin Venture acquired the Crossings at Lakeline, comprised of two three-story buildings containing an aggregate of 232,274 rentable square feet located in Austin, Texas for $48.2 million. The transaction was funded with $34.5 million of proceeds of a 3.87% fixed rate mortgage loan from a non-affiliated institutional lender and $12.8 million (net of $0.9 million in purchase adjustments) of cash capital contributions, with $6.4 million made by each of DRA and the Company. The Austin Venture expensed approximately $0.1 million of transaction costs to acquire the property, net of $0.6 million credit from the seller. On October 17, 2014, the Austin Venture acquired River Place, comprised of seven Class A office buildings containing 590,881 rentable square feet located in Austin, Texas for $128.1 million. The transaction was funded through a combination of an $88.0 million short-term loan, secured by a mortgage, made by the Company to the Austin Venture and cash capital contributions of $18.9 million made by each of DRA and the Company to the Austin Venture. The short-term financing was provided by the Company while the Austin Venture secured permanent financing. As of December 31, 2014, the Company accounted the short-term financing as a note receivable. On January 30, 2015, the Austin Venture closed on a mortgage loan with a non-affiliated institutional lender, and used the proceeds of the loan to repay in full an $88.0 million short-term secured loan made by the Company to fund costs of the Austin Venture's acquisition of River Place. The Austin Venture expensed approximately $0.2 million of transaction costs to acquire the property. 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 the Austin Venture. On October 18, 2017, the Austin Venture sold eight office properties in Austin, Texas containing 1,164,496 square feet for a gross sales price of $333.3 million. Seven of the properties were encumbered by $151.0 million of mortgage debt. The Company’s share of cash proceeds, after payment of the of the mortgage debt, closing costs and prorations, was $86.4 million. The Company’s share of the Austin Venture’s gain on sale was $40.1 million. Additionally, the Company recognized a deferred gain on sale of $12.1 million, which was established on the Company’s consolidated balance sheets when certain assets were contributed to the Austin Venture on October 16, 2013. In accordance with the relevant guidance for the sales of real estate, the contributed properties qualified as a partial sale and a portion of the gain was deferred and accreted. The Company met the criteria to recognize the unaccreted portion of the deferred gain on the partial sale as the sales process was complete upon the Austin Venture selling the properties to a third party. The summary of the transaction is as follows (in thousands); October 18, 2017 Gross sales price $ 333,250 Debt principal (150,968 ) Debt prepayment penalties (2,120 ) Closing costs and net prorations (7,420 ) Cash to Austin Venture $ 172,742 Company's ownership interest 50 % Cash to the Company $ 86,371 Cash to Austin Venture $ 172,742 Austin Venture basis of sold properties (92,559 ) Austin Venture gain on sale $ 80,183 Company's ownership interest 50 % Company's share of gain $ 40,092 Company's share of gain $ 40,092 Deferred gain from partial sale 12,072 Gain on real estate venture transactions $ 52,164 On December 11, 2018, the Company acquired DRA’s 50% ownership interest in the DRA Austin Venture for an aggregate purchase price of $535.1 million. The DRA Austin Venture owned twelve office properties containing an aggregate 1,570,123 square feet, located in Austin, Texas. See Note 3, " Real Estate Investments Brandywine - AI Venture: Station Square Impairment On July 10, 2012, Brandywine – AI Venture (the “AISS Venture”), an unconsolidated real estate venture in which the Company owns a 50% interest, acquired a three building office portfolio totaling 497,896 net rentable square feet in Silver Spring, Maryland, known as Station Square, valued at $ 120.6 million. During the period ended September 30, 2016, the AISS Venture recorded a $ 10.4 million held for use impairment charge related to Station Square, which is included in the Company’s Metropolitan D.C. segment. The Company's share of this impairment charge was $ 5.2 million and is reflected in equity in loss of Real Estate Ventures in its consolidated statement of operations for the period ended December 31, 2016. The fair value of the Station Square properties was primarily determined based on offers received for the properties . The remaining properties in the AISS Venture were evaluated for impairment, and based on an undiscounted cash flow analysis, no additional other than temporary impairment was identified. All of the inputs used to determine the above-mentioned impairment charges are categorized Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The Company evaluated for other than temporary impairment in its investment in the AISS Venture in accordance with ASC 323, “ Brandywine - AI Venture: Station Square and 7101 Wisconsin Avenue On December 28, 2018, the BDN – AI Venture sold three properties containing an aggregate of 510,202 rentable square feet located in Silver Spring, Maryland (“Station Square”), for a gross sales price of $107.0 million. At the time of sale, the properties were encumbered by a $66.5 million first mortgage financing, which was repaid in full at closing, resulting in a debt prepayment penalty of $0.7 million. Net of the first mortgage payoff and closing costs, BDN – AI Venture received cash proceeds of $34.8 million. For the Company’s 50% interest in BDN – AI Venture, it received net cash proceeds of $17.4 million and recognized a $1.5 million gain on the sale. Subsequent to the sale transaction, the BDN – AI Venture continues to own two properties containing an aggregate of 364,277 rentable square feet. On September 14, 2017, the BDN – AI Venture sold 7101 Wisconsin Avenue, a property containing 230,904 rentable square feet located in Bethesda, Maryland, for a gross sales price of $105.7 million. At the time of sale, the property was encumbered by $37.4 million first mortgage financing, which was repaid in full at closing, resulting in a debt prepayment penalty of $0.8 million. Net of the first mortgage payoff and closing costs, BDN – AI Venture received cash proceeds of $63.6 million. For the Company’s 50% interest, it received net cash proceeds of $31.8 million and recognized a $13.8 million gain on the sale transaction. Subsequent to the sale transaction, the BDN-AI Venture continued to own five properties containing an aggregate of 874,479 rentable square feet. Brandywine - AI Venture: Fairview Park Drive Impairment During the period ended December 31, 2018, the BDN – AI Venture recorded a $20.8 million held for use impairment charge related to 3141 Fairview Park Drive and 3130 Fairview Park Drive (the “Fairview Properties”). As of December 31, 2018, after the $20.8 million impairment charge, the carrying value of the properties was $50.4 million. The Company’s share of this impairment charge was $10.4 million and is reflected in the “Equity in loss of Real Estate Ventures” caption in the consolidated statements of operations for the period ended December 31, 2018. Subsequent to recording this impairment charge, the Company had a net basis of $15.8 million in the venture. The BDN – AI Venture measured this impairment based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 8.00% and 9.50% for 3130 Fairview Park Drive, and 8.00% and 8.00% for 3141 Fairview Park Drive, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The Company evaluated for other than temporary impairment in its investment in the BDN – AI Venture in accordance with ASC 323, Investments - Equity Method and Joint Ventures Brandywine - AI Venture: Other Than Temporary Impairment” Brandywine - AI Venture: Other Than Temporary Impairment As of December 31, 2018, the Company evaluated the recoverability of its investment basis in BDN – AI Venture utilizing a discounted cash flow model. Based on the Company’s evaluation of the fair value of the Company’s investment in the two properties that remained owned by the BDN – AI Venture subsequent to the disposition of Station Square, the Company determined that a persistent weak demand for office space and intense competition for tenants at the Fairview Properties had reduced the Company’s share of the fair value of the remaining properties to be less than its investment basis in BDN – AI Venture. As a result, the Company concluded that the decline in value was other than temporary. As of December 31, 2018, subsequent to recording a $4.1 million impairment charge, which was recorded within the “Equity in Loss of Real Estate Ventures” caption in the consolidated statements of operations, the Company had a net basis of $11.7 million in the venture. Determining the current fair value of the Company’s investment is based on a number of factors that are difficult to predict. The market may decline further and future impairment charges may be needed. The Company measured this impairment based on a discounted cash flow analysis, using a hold period of 10 years, a residual capitalization rate of 8.0% and discount rates ranging from 9.0% to 9.5%. The assumptions to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” As of September 30, 2017, the Company evaluated the recoverability of its investment basis in BDN – AI Venture utilizing a discounted cash flow model. Based on the Company’s evaluation of the fair value of the Company’s investment in the five properties that remained owned by the BDN – AI Venture subsequent to the disposition of 7101 Wisconsin Avenue, the Company determined that a persistent weak demand office for space and intense competition for tenants had reduced the Company’s share of the fair value of the remaining properties to be less than its investment basis in BDN – AI Venture. As a result, the Company concluded that the decline in value was other than temporary. As of September 30, 2017, subsequent to recording a $4.8 million other than temporary impairment charge, which was recorded within the “Equity in Loss of Real Estate Ventures” caption in the consolidated statements of operations, the Company had a net basis of $44.3 million in the venture. The Company measured this impairment based on a discounted cash flow analysis, using a hold period of 10 years, a residual capitalization rate of 7.5% and discount rates ranging from 7.8% to 8.5%. The assumptions to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” MAP Venture On February 4, 2016, Brandywine Operating Partnership, L.P., together with subsidiaries of the Operating Partnership, entered into a series of related transactions (the “Och-Ziff Sale”) with affiliates of Och-Ziff Capital Management Group LLC (“Och-Ziff”) that resulted in the disposition by the Company of 58 office properties that contain an aggregate of 3,924,783 square feet for an aggregate purchase price of $398.1 million. The 58 properties are located in the Pennsylvania Suburbs, New Jersey/Delaware, Metropolitan Washington, D.C. and Richmond, Virginia. The related transactions involved: (i) the sale by the Company to MAP Fee Owner LLC, an affiliate of Och-Ziff (the “O-Z Land Purchaser”), of 100% of the Company’s fee interests in the land parcels (the “Land Parcels”) underlying the 58 office properties, together with rights to be the lessor under long-term ground leases (the “Ground Leases”) covering the Land Parcels and; (ii) the Company’s formation of MAP Ground Lease Venture LLC (the “MAP Venture”) with MAP Ground Lease Holdings The MAP Venture leases the Land Parcels through a ground lease that extends through February 2115. 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. Thereafter, annual rental payments increase by 2.5% or CPI at the discretion of the lessor. At closing on February 4, 2016, the MAP Venture obtained a third party non-recourse debt financing of approximately $180.8 million secured by mortgages on the Buildings of the MAP Venture. As a result of this transaction, the Company received $354.0 million in proceeds and maintains a 50% ownership interest in the MAP Venture valued as of February 4, 2016 at $25.2 million, which holds the leasehold interest in the Buildings. The MAP Venture was formed as a limited liability company in which the Company has been designated as the Managing Member. In addition, through an affiliate, the Company provides property management services at the Buildings on behalf of the MAP Venture for a market based management fee. On August 1, 2018, MAP Venture refinanced its $180.8 million third party debt financing, secured by the buildings of MAP Venture and maturing February 9, 2019, with $185.0 million third party debt financing, also secured by the buildings, bearing interest at LIBOR + 2.45% capped at a total maximum interest of 6.00% and maturing on August 1, 2023. The Company accounts for its investment in the MAP Venture under the equity method of accounting. Based upon the reconsideration event caused by the refinancing of the MAP Venture’s third party debt financing, the Company reassessed its consolidation conclusion. The Company determined that this Real Estate Venture is no longer a VIE in accordance with the accounting standard for the consolidation of VIEs because MAP Venture, through the refinancing of the third-party debt financing and without further support from the Company or its partner in the venture, demonstrated that it has sufficient equity at risk to finance its activities. As a result, the Company is using the voting interest model under the accounting standard for consolidation in order to determine whether to consolidate MAP Venture. Based upon each member's substantive participating rights over the activities that significantly impact the operations and revenues of MAP Venture under the operating agreement and related agreements, MAP Venture is not consolidated by the Company, and is accounted for under the equity method of accounting. As a result of this transaction, the Company did not gain a controlling financial interest over MAP Venture; therefore, it was not required to remeasure its previously held equity interest to fair value. Brandywine 1919 Ventures On January 20, 2011, the Company acquired a one acre parcel of land in Philadelphia, Pennsylvania for $9.3 million. The Company thereafter contributed the acquired land into a then newly-formed general partnership, referred to as “1919 Ventures” in return for a 50.0% general partner interest, with the remaining 50% interest

Deferred Costs

Deferred Costs	12 Months Ended
	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
DEFERRED COSTS	5. DEFERRED COSTS As of December 31, 2018 and 2017, the Company’s deferred costs (assets) were comprised of the following (in thousands): December 31, 2018 Total Cost Amortization Deferred Costs, net Leasing costs $ 144,831 $ (56,846 ) $ 87,985 Financing costs - Revolving Credit Facility 6,298 (3,208 ) 3,090 Total $ 151,129 $ (60,054 ) $ 91,075 December 31, 2017 Total Cost Accumulated Amortization Deferred Costs, net Leasing costs $ 154,481 $ (59,046 ) $ 95,435 Financing costs - Revolving Credit Facility 3,595 (2,335 ) 1,260 Total $ 158,076 $ (61,381 ) $ 96,695 During the years ended December 31, 2018, 2017 and 2016, the Company capitalized internal direct leasing costs of $3.9 million, $4.6 million and $5.0 million, respectively, in accordance with the accounting standard for the capitalization of leasing costs.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS	6. INTANGIBLE ASSETS As of December 31, 2018 and 2017, the Company’s intangible assets were comprised of the following (in thousands): December 31, 2018 Total Cost Accumulated Amortization Intangible Assets, net Intangible assets, net: In-place lease value $ 181,887 $ (53,376 ) $ 128,511 Tenant relationship value $ 9,564 (8,551 ) 1,013 Above market leases acquired $ 4,966 (3,142 ) 1,824 Total intangible assets, net $ 196,417 $ (65,069 ) $ 131,348 Acquired lease intangibles, net: Below market leases acquired $ 49,655 $ (17,872 ) $ 31,783 December 31, 2017 Total Cost Accumulated Amortization Intangible Assets, net Intangible assets, net: In-place lease value $ 108,060 $ (47,003 ) $ 61,057 Tenant relationship value 11,201 (9,275 ) 1,926 Above market leases acquired 4,545 (2,556 ) 1,989 Total intangible assets, net $ 123,806 $ (58,834 ) $ 64,972 Acquired lease intangibles, net: Below market leases acquired $ 36,213 $ (15,939 ) $ 20,274 For the year ended December 31, 2018 the Company accelerated the amortization of intangible assets by approximately $0.7 million as a result of tenant move-outs prior to the end of the associated lease term. For each of the years ended December 31, 2017 and 2016, this amount was $0.6 million. For the years ended December 31, 2018, 2017, and 2016, the Company accelerated the amortization of a nominal amount of intangible liabilities as a result of tenant move-outs. As of December 31, 2018, the Company’s annual amortization for its intangible assets/liabilities, assuming no early lease terminations, are as follows (dollars in thousands): Assets Liabilities 2019 $ 41,968 $ 7,403 2020 28,393 5,707 2021 20,128 4,302 2022 12,791 2,654 2023 9,756 2,094 Thereafter 18,312 9,623 Total $ 131,348 $ 31,783

Debt Obligations

Debt Obligations	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
DEBT OBLIGATIONS	7. DEBT OBLIGATIONS The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at December 31, 2018 and 2017 (in thousands): December 31, 2018 December 31, 2017 Effective Interest Rate Maturity Date MORTGAGE DEBT: Two Logan Square $ 82,805 $ 84,440 3.98% May 2020 Four Tower Bridge 9,526 - 4.50% (a) Feb 2021 One Commerce Square 120,183 123,667 3.64% Apr 2023 Two Commerce Square 110,518 112,000 4.51% Apr 2023 Principal balance outstanding 323,032 320,107 Plus: fair market value premium (discount), net (1,759 ) (2,325 ) Less: deferred financing costs (404 ) (566 ) Mortgage indebtedness $ 320,869 $ 317,216 UNSECURED DEBT $600 million Unsecured Credit Facility $ 92,500 $ - LIBOR + 1.10% Jul 2022 Seven-Year Term Loan - Swapped to fixed 250,000 250,000 2.87% (b) Oct 2022 $350.0M 3.95% Guaranteed Notes due 2023 350,000 350,000 3.87% Feb 2023 $250.0M 4.10% Guaranteed Notes due 2024 250,000 250,000 4.33% Oct 2024 $450.0M 3.95% Guaranteed Notes due 2027 450,000 450,000 4.03% Nov 2027 $250.0M 4.55% Guaranteed Notes due 2029 250,000 250,000 4.60% Oct 2029 Indenture IA (Preferred Trust I) 27,062 27,062 LIBOR + 1.25% Mar 2035 Indenture IB (Preferred Trust I) - Swapped to fixed 25,774 25,774 3.30% Apr 2035 Indenture II (Preferred Trust II) - Swapped to fixed 25,774 25,774 3.09% Jul 2035 Principal balance outstanding 1,721,110 1,628,610 Plus: original issue premium (discount), net (4,096 ) (4,423 ) Less: deferred financing costs (9,837 ) (10,575 ) Total unsecured indebtedness $ 1,707,177 $ 1,613,612 Total Debt Obligations $ 2,028,046 $ 1,930,828 (a) This loan was assumed upon acquisition of the related property on January 5, 2018. The interest rate reflects the market rate at the time of acquisition. (b) On December 13, 2018, the Company amended and restated its $250.0 million seven-year term loan maturing October 8, 2022. In connection with the terms of the amendment, the credit spread on the term loan decreased from LIBOR plus 1.80% to LIBOR plus 1.25%, reducing the Company’s effective interest rate by 0.55%. Through a series of interest rate swaps, the $250.0 million outstanding balance of the term loan has a fixed interest rate of 2.87%. During 2018, 2017, and 2016, the Company’s weighted-average effective interest rate on its mortgage notes payable was 4.05%, 4.04%, and 4.03%, respectively. The Parent Company unconditionally guarantees the unsecured debt obligations of the Operating Partnership (or is a co-borrower with the Operating Partnership) but does not by itself incur unsecured indebtedness. The Parent Company has no material assets other than its investment in the Operating Partnership. On July 17, 2018, the Company amended and restated its revolving credit agreement (as amended and restated, the “2018 Credit Facility”). The amendment and restatement, among other things: (i) maintained the total commitment of the revolving line of credit of $600.0 million; (ii) extended the maturity date from May 15, 2019 to July 15, 2022, with two six-month extensions at the Company’s election subject to specified conditions and subject to payment of an extension fee; (iii) reduced the interest rate margins applicable to Eurodollar loans; (iv) provided for an additional interest rate option based on a floating LIBOR rate; and (v) removed the covenant requiring the Company to maintain a minimum net worth. In connection with the amendments, the Company capitalized $2.7 million in financing costs, which will be amortized through the July 15, 2022 maturity date. competitive bid option that allows banks that are part of the lender consortium to bid to make loan advances to the Company at a reduced interest rate. In addition, the Company is also obligated to pay (1) in quarterly installments a facility fee on the total commitment at a rate per annum ranging from 0.125 % to 0.30 % based on the Company's credit rating and (2) an annual fee on the undrawn amount of each letter or credit equal to the LIBOR Margin. Based on the Company's current credit rating, the LIBOR margin is 1.10 % and the facility fee is 0.25 %. The terms of the 2018 Credit Facility require that the Company maintain customary financial and other covenants, including: (i) a fixed charge coverage ratio greater than or equal to 1.5 to 1.00; (ii) a leverage ratio less than or equal to 0.60 to 1.00, subject to specified exceptions; (iii) a ratio of unsecured indebtedness to unencumbered asset value less than or equal to 0.60 to 1.00, subject to specified exceptions; (iv) a ratio of secured indebtedness to total asset value less than or equal to 0.40 to 1.00; and (v) a ratio of unencumbered cash flow to interest expense on unsecured debt greater than 1.75 to 1.00. In addition, the 2018 Credit Facility restricts payments of dividends and distributions on shares in excess of 95% of the Company's funds from operations (FFO) except to the extent necessary to enable the Company to continue to qualify as a REIT for Federal income tax purposes. The Company had $92.5 million of borrowings under the 2018 Credit Facility as of the twelve-month period ended December 31, 2018. During the twelve months ended December 31, 2018, the weighted-average interest rate on 2018 Credit Facility borrowings was 3.24% resulting in $1.0 million of interest expense. As of December 31, 2018, the effective interest rate on 2018 Credit Facility borrowings was 3.61%. As of December 31, 2017, the Company had no borrowings under the Credit Facility. During the twelve months ended December 31, 2017, the weighted-average interest rate on Credit Facility borrowings was 2.28% resulting in $2.6 million of interest expense. On November 17, 2017, the Company completed an underwriting offering of its $450.0 million 3.95% Guaranteed Notes due 2027 (the “2027 Notes”) and reopened the 3.95% Guaranteed Notes due 2023 (the “2023 Notes”) for an additional $100.0 million. The 2027 Notes were priced at 99.25% of their face amount with a yield to maturity of 4.04%, representing a spread at the time of pricing of 1.70% over the ten-year treasury rate. The 2023 Notes were priced at 102.497% of their face amount with a yield to maturity of 3.40%, representing a spread at the time of pricing of 1.40% over the five-year treasury rate. The 2027 Notes and 2023 Notes have been reflected net of a discount of $3.4 million and a premium of $2.5 million, respectively, in the consolidated balance sheet as of December 31, 2017. The Company received $546.6 million after the deduction for underwriting discounts and offering expenses. On November 17, 2017, the Company used a portion of the net proceeds from the offering of the 2027 Notes and 2023 Notes to repurchase $115.1 million aggregate principal amount of 2018 Notes, through a tender offer, which consists of a $113.4 million principal repayment of the 2018 Notes, $1.2 million of prepayment penalties and $0.5 million of accrued interest. The Company recognized a $1.4 million loss on early extinguishment of debt related to the total repurchase. On December 18, 2017, the Company redeemed in full the $211.6 million aggregate principal amount of 2018 Notes that remained outstanding following completion of the tender offer, at a cash redemption price of $215.7 million (inclusive of prepayment penalties of $2.3 million and accrued interest of $1.8 million). The Company recognized a $2.5 million loss on early extinguishment of debt related to the total repurchase. The following table provides additional information on the Company’s repurchase of $325.0 million in the aggregate principal amount of its outstanding unsecured notes (consisting of the 2018 Notes, as indicated above) during the twelve months ended December 31, 2017 (in thousands). There were no repurchases of unsecured debt during the twelve months ended December 31, 2018 or 2016. Notes Principal Repurchase Amount (a) Loss on Early Extinguishment of Debt (b) 2018 4.95% Notes $ 325,000 $ 330,792 $ (3,933 ) (a) Includes prepayment penalties with respect to the redemption of debt. (b) Includes unamortized balance of the original issue discount and deferred financing costs. The Company was in compliance with all financial covenants as of December 31, 2018. Management continuously monitors the Company’s compliance with and anticipated compliance with the covenants. Certain of the covenants restrict the Company’s ability to obtain alternative sources of capital. While the Company currently believes it will remain in compliance with its covenants, in the event that the economy deteriorates in the future, the Company may not be able to remain in compliance with such covenants, in which case a default would result absent a lender waiver. As of December 31, 2018, the Company’s aggregate scheduled principal payments of debt obligations, excluding amortization of discounts and premiums, are as follows (in thousands): 2019 $ 7,595 2020 87,226 2021 15,143 2022 348,832 2023 556,736 Thereafter 1,028,610 Total principal payments 2,044,142 Net unamortized premiums/(discounts) (5,855 ) Net deferred financing costs (10,241 ) Outstanding indebtedness $ 2,028,046

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	8. FAIR VALUE OF FINANCIAL INSTRUMENTS The Company determined the fair values disclosed below using available market information and discounted cash flow analyses as of December 31, 2018 and 2017, respectively. The discount rate used in calculating fair value is the sum of the current risk free rate and the risk premium on the date of measurement of the instruments or obligations. Considerable judgment is necessary to interpret market data and to develop the related estimates of fair value. Accordingly, the estimates presented are not necessarily indicative of the amounts that the Company could realize upon disposition. The use of different estimation methodologies may have a material effect on the estimated fair value amounts shown. The Company believes that the carrying amounts reflected in the consolidated balance sheets at December 31, 2018 and 2017 approximate the fair values for cash and cash equivalents, accounts receivable, other assets, accounts payable and accrued expenses because they are short-term in duration. The following are financial instruments for which the Company’s estimates of fair value differ from the carrying amounts (in thousands): December 31, 2018 December 31, 2017 Carrying Amount (a) Fair Value Carrying Amount (a) Fair Value Unsecured notes payable $ 1,288,024 $ 1,262,570 $ 1,286,573 $ 1,314,900 Variable rate debt $ 419,153 $ 402,924 $ 327,039 $ 308,872 Mortgage notes payable $ 320,869 $ 318,515 $ 317,216 $ 304,665 Notes receivable (b) $ 47,771 $ 47,747 $ 3,532 $ 3,605 (a) T he carrying amounts presented in the table above are net of deferred financing costs of $7.9 million and $8.9 million for unsecured notes payable, $5.1 million and $1.3 million for variable rate debt and $0.4 million and $0.6 million for mortgage notes payable as of December 31, 2018 and December 31, 2017, respectively. (b) The inputs to originate the notes receivable are unobservable and, as a result, are categorized as Level 3. The Company determined fair value by calculating the present value of the cash payments to be received through the maturity date of the loans. On June 26, 2018, the Company provided a $44.4 million mortgage loan to Brandywine 1919 Ventures, an unconsolidated real estate venture in which the Company holds a 50% ownership interest, and recorded a note receivable of $44.4 million. For additional information regarding the transaction, see Note 4, “ Investment in Unconsolidated Real Estate Ventures As of December 31, 2018, notes receivable also consisted of a $3.4 million note receivable that was provided to a third party to acquire a property. The mortgage bears interest at 7.0% through March 2019 and 8.0% interest thereafter until its maturity date in March of 2020. The loan principal amortizes down to the balloon payment of $3.1 million which the Company expects to receive at maturity of the note in March of 2020. The Company periodically assesses collectability of the notes receivable in accordance with the accounting standard for loan receivables. As of December 31, 2018, the Company’s notes receivable are collectible. The inputs utilized to determine the fair value of the Company’s unsecured notes payable are categorized as Level 2. This is because the Company valued these instruments using quoted market prices as of December 31, 2018 and December 31, 2017. For the fair value of the Company’s unsecured notes, the Company uses a discount rate based on the indicative new issue pricing provided by lenders. The inputs utilized to determine the fair value of the Company’s mortgage notes payable and variable rate debt are categorized as Level 3. The fair value of the variable rate debt was estimated using a discounted cash flow analysis valuation on the borrowing rates currently available to the Company for loans with similar terms and maturities, as applicable. The fair value of the mortgage debt was determined by discounting the future contractual interest and principal payments by a blended market rate for loans with similar terms, maturities and loan-to-value. These inputs have been categorized as Level 3 because the Company considers the rates used in the valuation techniques to be unobservable inputs. The inputs to originate the notes receivable are unobservable and, as a result, are categorized as Level 3. The Company determined fair value by calculating the present value of the cash payments to be received through the maturity dates of the loans. For the Company’s mortgage loans, the Company uses an estimate based discounted cash flow analyses and its knowledge of the mortgage market. An increase in the discount rate used in the discounted cash flow model would result in a decrease in the fair value of the Company’s long-term debt. Conversely, a decrease in the discount rate used in the discounted cash flow model would result in an increase in the fair value of the Company’s long-term debt. Disclosure about the fair value of financial instruments is based upon pertinent information available to management as of December 31, 2018 and December 31, 2017. Although management is not aware of any factors that would significantly affect the fair value amounts, such amounts were not comprehensively revalued for purposes of these financial statements since December 31, 2018. Current estimates of fair value may differ from the amounts presented herein.

Risk Management and Use of Deri

Risk Management and Use of Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
RISK MANAGEMENT AND USE OF DERIVATIVE FINANCIAL INSTRUMENTS	9. RISK MANAGEMENT AND USE OF DERIVATIVE FINANCIAL INSTRUMENTS Risk Management In the course of its ongoing business operations, the Company encounters economic risk. There are three main components of economic risk: interest rate risk, credit risk, and market risk. The Company is subject to interest rate risk on its interest-bearing liabilities. Credit risk is primarily the risk of inability or unwillingness of tenants to make contractually required payments and of counterparties on derivatives contracts to fulfill their obligations. Market risk is the risk of declines in the value of Company properties due to changes in rental rates, interest rates, supply and demand of similar products and other market factors affecting the valuation of properties. Risks and Uncertainties In the U.S., market and economic conditions have been improving, resulting in an increase of the volume of real estate transactions in the market. If the economy deteriorates, vacancy rates may increase through 2019 and possibly beyond. The financial markets also have an effect on the Company’s Real Estate Venture partners and contractual counterparties, including counterparties in derivative contracts. The Company’s Credit Facility, term loans and the indenture governing its unsecured public debt securities (See Note 7, “ Debt Obligations Availability of borrowings under the unsecured revolving credit facility is subject to a traditional material adverse effect clause. Each time the Company borrows it must represent to the lenders that there have been no events of a nature which would have a material adverse effect on the business, assets, operations, condition (financial or otherwise) or prospects of the Company taken as a whole or which could negatively affect the ability of the Company to perform its obligations under the unsecured revolving credit facility. While the Company believes that there are currently no material adverse effect events, it is possible that such an event could arise which would limit the Company’s borrowings under the unsecured revolving credit facility. If an event occurs which is considered to have a material adverse effect, the lenders could consider the Company in default under the terms of the unsecured revolving credit facility and any borrowings under the unsecured revolving credit facility would become unavailable. If the Company is unable to obtain a waiver, this would have a material adverse effect on the Company’s financial position and results of operations. The Company was in compliance with all financial covenants as of December 31, 2018. Management continuously monitors the Company’s compliance with and anticipated compliance with the covenants. Certain of the covenants restrict management’s ability to obtain alternative sources of capital. While the Company currently believes it will remain in compliance with its covenants, in the event that the economy deteriorates in the future, the Company may not be able to remain in compliance with such covenants, in which case a default would result absent a lender waiver. Use of Derivative Financial Instruments The Company’s use of derivative instruments is limited to the utilization of interest rate agreements or other instruments to manage interest rate risk exposures and not for speculative purposes. The principal objective of such arrangements is to minimize the risks and/or costs associated with the Company’s operating and financial structure, as well as to hedge specific transactions. The counterparties to these arrangements are major financial institutions with which the Company and its affiliates may also have other financial relationships. The Company is potentially exposed to credit loss in the event of non-performance by these counterparties. However, because of the high credit ratings of the counterparties, the Company does not anticipate that any of the counterparties will fail to meet these obligations as they come due. The Company does not hedge credit or property value market risks through derivative financial instruments. The Company formally assesses, both at the inception of a hedge and on an on-going basis, whether each derivative is highly-effective in offsetting changes in cash flows of the hedged item. If management determines that a derivative is not highly-effective as a hedge or if a derivative ceases to be a highly-effective hedge, the Company will discontinue hedge accounting prospectively for either the entire hedge or the portion of the hedge that is determined to be ineffective. The related ineffectiveness would be charged to the consolidated statement of operations. The valuation of these instruments is determined using widely accepted valuation techniques including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves and implied volatilities. The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) and the discounted expected variable cash payments (or receipts). The variable cash payments (or receipts) are based on an expectation of future interest rates (forward curves) derived from observable market interest rate curves. To comply with the provisions of the accounting standard for fair value measurements and disclosures, the Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees. The following table summarizes the terms and fair values of the Company’s derivative financial instruments as of December 31, 2018 and December 31, 2017. The notional amounts provide an indication of the extent of the Company’s involvement in these instruments at that time but do not represent exposure to credit, interest rate or market risks (amounts presented in thousands). Hedge Product Hedge Type Designation Notional Amount Strike Trade Date Maturity Date Fair value 12/31/2018 12/31/2017 12/31/2018 12/31/2017 Assets Swap Interest Rate Cash Flow (a) $ 250,000 $ 250,000 2.868 % October 8, 2015 October 8, 2022 $ 7,008 $ 5,694 Swap Interest Rate Cash Flow (a) 25,774 25,774 3.300 % December 22, 2011 January 30, 2021 292 25 Swap Interest Rate Cash Flow (a) 25,774 25,774 3.090 % January 6, 2012 October 30, 2019 183 59 $ 301,548 $ 301,548 (a) Hedging unsecured variable rate debt. The Company measures its derivative instruments at fair value and records them in the “Other assets” and (“Other liabilities”) captions on the Company’s consolidated balance sheets. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by itself and its counterparties. The Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Company has determined that the inputs utilized to determine the fair value of derivative instruments are classified in Level 2 of the fair value hierarchy. Disclosure about the fair value of derivative instruments is based upon pertinent information available to management as of December 31, 2018 and December 31, 2017. Although management is not aware of any factors that would significantly affect the fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since December 31, 2018. Current estimates of fair value may differ from the amounts presented herein. Concentration of Credit Risk Concentrations of credit risk arise for the Company when multiple tenants of the Company are engaged in similar business activities, or are located in the same geographic region, or have similar economic features that impact in a similar manner their ability to meet contractual obligations, including those to the Company. The Company regularly monitors its tenant base to assess potential concentrations of credit risk. Management believes the current credit risk portfolio is reasonably well diversified and does not contain an unusual concentration of credit risk. No tenant accounted for 10% or more of the Company’s rents during 2018, 2017 and 2016. Conditions in the general economy and the global credit markets have had a significant adverse effect on numerous industries. The Company has tenants concentrated in various industries that may be experiencing adverse effects from the current economic conditions and the Company could be adversely affected if such tenants were to default under their leases.

Limited Partners' NonControllin

Limited Partners' NonControlling Interests in the Parent Company	12 Months Ended
	Dec. 31, 2018
Noncontrolling Interest [Abstract]
LIMITED PARTNERS' NONCONTROLLING INTERESTS IN THE PARENT COMPANY	10. LIMITED PARTNERS’ NONCONTROLLING INTERESTS IN THE PARENT COMPANY Noncontrolling interests in the Parent Company’s financial statements relate to redeemable common limited partnership interests in the Operating Partnership held by parties other than the Parent Company and properties which are consolidated but not wholly owned. Operating Partnership The aggregate book value of the noncontrolling interests associated with the redeemable common limited partnership interests that were consolidated in the accompanying consolidated balance sheet of the Parent Company as of December 31, 2018 and December 31, 2017, was $10.1 million and $15.2 million, respectively. Under the applicable accounting guidance, the redemption value of limited partnership units are carried at, on a limited partner basis, the greater of historical cost adjusted for the allocation of income and distributions or fair value. The Parent Company believes that the aggregate settlement value of these interests (based on the number of units outstanding and the closing price of the common shares on the balance sheet date) was approximately $12.6 million and $26.9 million, respectively, as of December 31, 2018 and December 31, 2017.

Beneficiaries Equity of the Par

Beneficiaries Equity of the Parent Company	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
BENEFICIARIES' EQUITY OF THE PARENT COMPANY	11. BENEFICIARIES’ EQUITY OF THE PARENT COMPANY Earnings per Share (EPS) The following tables detail the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding): Year ended December 31, 2018 2017 2016 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 137,289 $ 137,289 $ 121,859 $ 121,859 $ 40,501 $ 40,501 Net income attributable to noncontrolling interests (965 ) (965 ) (1,009 ) (1,009 ) (310 ) (310 ) Nonforfeitable dividends allocated to unvested restricted shareholders (369 ) (369 ) (327 ) (327 ) (341 ) (341 ) Distribution to preferred shareholders - - (2,032 ) (2,032 ) (6,900 ) (6,900 ) Preferred share redemption charge - - (3,181 ) (3,181 ) - - Net income attributable to common shareholders $ 135,955 $ 135,955 $ 115,310 $ 115,310 $ 32,950 $ 32,950 Denominator Weighted-average shares outstanding 178,519,748 178,519,748 175,484,350 175,484,350 175,018,163 175,018,163 Contingent securities/Share based compensation - 1,121,744 - 1,323,816 - 992,651 Weighted-average shares outstanding 178,519,748 179,641,492 175,484,350 176,808,166 175,018,163 176,010,814 Earnings per Common Share: Net income attributable to common shareholders $ 0.76 $ 0.76 $ 0.66 $ 0.65 $ 0.19 $ 0.19 The contingent securities/share based compensation impact is calculated using the treasury stock method and relates to employee awards settled in shares of the Parent Company. The effect of these securities is anti-dilutive for periods that the Parent Company incurs a net loss from continuing operations available to common shareholders and therefore is excluded from the dilutive earnings per share calculation in such periods. Redeemable common limited partnership units, totaling 982,871 in 2018, and 1,479,799 in both 2017 and 2016, were excluded from the diluted earnings per share computations because they are not dilutive. Unvested restricted shares are considered participating securities which require the use of the two-class method for the computation of basic and diluted earnings per share. For the years ended December 31, 2018, 2017 and 2016, earnings representing nonforfeitable dividends were allocated to the unvested restricted shares issued to the Company’s executives and other employees under the Amended and Restated 1997 Long-Term Incentive Plan. Common and Preferred Shares On December 6, 2018, the Parent Company declared a distribution of $0.19 per common share, totaling $33.6 million, which was paid on January 22, 2019 to shareholders of record as of January 8, 2019. Of the 20,000,000 preferred shares authorized, none were outstanding as of December 31, 2018 or December 31, 2017. On April 11, 2017, the Parent Company redeemed all of its outstanding 4,000,000 Series E Preferred Shares at an aggregate redemption price of $25.51 per share, which includes $2.0 million of dividends accrued through the redemption date. The redemption was funded with existing cash balances on hand. Also on April 11, 2017, the Parent Company recognized a $3.2 million charge related to the underwriting discount and related expenses incurred at issuance of the Series E Preferred Shares on April 11, 2012. This charge is included in the earnings per share calculations above, as well as within the Parent Company’s consolidated statements of operations as a reduction in net income to arrive at net income attributable to common shareholders under the caption “Preferred share redemption charge.” There were no comparable charges for the years ended December 31, 2018 or 2016. Common Share Repurchases The Parent Company maintains a common share repurchase program under which the Board of Trustees has authorized the Parent Company to repurchase common shares. On January 3, 2019, the Board of Trustees replenished this program by authorizing the Parent Company to repurchase up to $150 million common shares under the program from and after January 3, 2019. During the year ended 2018, the Company repurchased and retired 1,729,278 common shares at an average price of $12.64 per share, totaling $21.9 million. During the years ended December 31, 2017 and 2016, there were no share repurchases under the program. The Company expects to fund any additional share repurchases with a combination of available cash balances and availability under its unsecured revolving credit facility. The timing and amounts of any repurchases will depend on a variety of factors, including market conditions, regulatory requirements, share prices, capital availability and other factors as determined by the Company’s management team. The repurchase program does not require the purchase of any minimum number of shares and may be suspended or discontinued at any time without notice. In connection with the Parent Company’s common share repurchase program, one common unit of the Operating Partnership is retired for each common share repurchased. During the year ended December 31, 2018, the Company repurchased and retired 1,729,278 common units at an average price of $12.64 per unit, totaling $21.9 million. During the years ended December 31, 2017 and 2016, there were no unit repurchases under the program. The Company expects to fund any additional unit repurchases with a combination of available cash balances and availability under its unsecured revolving credit facility. The timing and amounts of any purchases will depend on a variety of factors, including market conditions, regulatory requirements, unit prices, capital availability and other factors as determined by the Company’s management team. The repurchase program does not require the purchase of any minimum number of units and may be suspended or discontinued at any time without notice. The common shares repurchased were retired and, as a result, were accounted for in accordance with Maryland law, which does not contemplate treasury stock. The repurchases were recorded as a reduction of common shares (at $0.01 par value per unit) and a decrease to General Partnership Capital. Continuous Offering Program On January 10, 2017, the Parent Company entered into a continuous offering program (the “Offering Program”), under which it may sell up to an aggregate of 16,000,000 common shares until January 10, 2020 in at-the-market offerings. In connection with the commencement of the Offering Program, $0.2 million of upfront costs were recorded to additional paid-in capital. This program is a replacement of a prior continuous offering program that expired on November 3, 2016. During 2018 and 2017, the Parent Company issued 23,311 and 2,858,991 common shares under the Offering Program at weighted average prices per share of $18.04 and $18.19, receiving net cash proceeds of $0.4 million and $51.2 million, respectively. No shares were issued during 2016 under the prior continuous offering program that expired on November 3, 2016. At December 31, 2018, 13,117,698 common shares remain available for issuance under the Offering Program.

Partners Equity of The Operatin

Partners Equity of The Operating Partnership	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
PARTNERS' EQUITY OF THE OPERATING PARTNERSHIP	12. PARTNERS’ EQUITY OF THE OPERATING PARTNERSHIP Earnings per Common Partnership Unit The following tables detail the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding): Year ended December 31, 2018 2017 2016 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 137,289 $ 137,289 $ 121,859 $ 121,859 $ 40,501 $ 40,501 Net income attributable to noncontrolling interests (55 ) (55 ) (29 ) (29 ) (15 ) (15 ) Nonforfeitable dividends allocated to unvested restricted unitholders (369 ) (369 ) (327 ) (327 ) (341 ) (341 ) Preferred unit dividends - - (2,032 ) (2,032 ) (6,900 ) (6,900 ) Preferred unit redemption charge - - (3,181 ) (3,181 ) - - Net income attributable to common unitholders $ 136,865 $ 136,865 $ 116,290 $ 116,290 $ 33,245 $ 33,245 Denominator Weighted-average units outstanding 179,959,370 179,959,370 176,964,149 176,964,149 176,523,800 176,523,800 Contingent securities/Share based compensation - 1,121,744 - 1,323,816 - 992,651 Total weighted-average units outstanding 179,959,370 181,081,114 176,964,149 178,287,965 176,523,800 177,516,451 Earnings per Common Partnership Unit: Net income attributable to common unitholders $ 0.76 $ 0.76 $ 0.66 $ 0.65 $ 0.19 $ 0.19 Unvested restricted units are considered participating securities which require the use of the two-class method for the computation of basic and diluted earnings per unit. For the years ended December 31, 2018, 2017 and 2016, earnings representing nonforfeitable dividends were allocated to the unvested restricted units issued to the Parent Company’s executives and other employees under the Parent Company’s shareholder-approved long-term incentive plan. Common Partnership Units and Preferred Mirror Units The Operating Partnership issues partnership units to the Parent Company in exchange for the contribution of the net proceeds of any equity security issuance by the Parent Company. The number and terms of such partnership units correspond to the number and terms of the related equity securities issued by the Parent Company. In addition, the Operating Partnership may also issue separate classes of partnership units. Historically, the Operating Partnership has had the following types of partnership units outstanding: (i) Preferred Partnership Units which have been issued to parties other than the Parent Company; (ii) Preferred Mirror Partnership Units which have been issued to the Parent Company; and (iii) Common Partnership Units which include both interests held by the Parent Company and those held by other limited partners. Preferred Mirror Partnership Units In exchange for the proceeds received in corresponding offerings by the Parent Company of preferred shares of beneficial interest, the Operating Partnership has issued to the Parent Company a corresponding amount of Preferred Mirror Partnership Units with terms consistent with that of the preferred securities issued by the Parent Company. No preferred units were outstanding as of December 31, 2018 or December 31, 2017. Common Partnership Units (Redeemable and General) The Operating Partnership has two classes of Common Partnership Units outstanding as of December 31, 2018: (i) Class A Limited Partnership Interest which are held by both the Parent Company and outside third parties and (ii) General Partnership Interests which are held solely by the Parent Company (collectively, the Class A Limited Partnership Interest, and General Partnership Interests are referred to as “Common Partnership Units”). The holders of the Common Partnership Units are entitled to share in cash distributions from, and in profits and losses of, the Operating Partnership, in proportion to their respective percentage interests, subject to preferential distributions on the preferred mirror units and the preferred units. The Common Partnership Units held by the Parent Company (comprised of both General Partnership Units and Class A Limited Partnership Units) are presented as partner’s equity in the consolidated financial statements. Class A Limited Partnership Interest held by parties other than the Parent Company are redeemable at the option of the holder for a like number of common shares of the Parent Company, or cash, or a combination thereof, at the election of the Parent Company. Because the form of settlement of these redemption rights are not within the control of the Operating Partnership, these Common Partnership Units have been excluded from partner’s equity and are presented as redeemable limited partnership units measured at the potential cash redemption value as of the end of the periods presented based on the closing market price of the Parent Company’s common shares at December 31, 2018 , 2017 and 2016 , which was $12.87 , $ 18.19 and $ 16.51 , respectively. As of December 31, 2018 , 982,871 Class A Units were outstanding and owned by outside limited partners of the Operating Partnership. As of both December 31, 2017 and 2016, 1,479,799 Class A Units were outstanding and owned by outside limited partners of the Operating Partnership. On December 6, 2018, the Operating Partnership declared a distribution of $0.19 per common unit, totaling $33.6 million, which was paid on January 22, 2019 to unitholders of record as of January 8, 2019. On April 11, 2017, the Operating Partnership redeemed all of its outstanding 4,000,000 Series E-Linked Preferred Mirror Units at an aggregate redemption price of $25.51 per unit, which includes $2.0 million of dividends accrued through the redemption date. The redemption of preferred units was funded with existing cash balances on hand. Also on April 11, 2017, the Operating Partnership recognized a $3.2 million charge related to the underwriting discount and related expenses incurred at issuance of the Series E-Linked Preferred Mirror Units on April 11, 2012. This charge is included in the earnings per share calculations above, as well as within the Operating Partnership’s consolidated statements of operations as a reduction in net income to arrive at net income attributable to common partnership unitholders under the caption “Preferred unit redemption charge.” There were no comparable charges for the years ended December 31, 2018 or 2016. Common Unit Repurchases In connection with the Parent Company’s common share repurchase program, one common unit of the Operating Partnership is retired for each common share repurchased. On January 3, 2019, the Board of Trustees replenished this program by authorizing the Parent Company to repurchase of up to $150.0 million common shares under the program from and after January 3, 2019. During the year ended December 31, 2018, the Company repurchased and retired 1,729,278 common units at an average price of $12.64 per unit, totaling $21.9 million. During the years ended December 31, 2017 and 2016, there were no unit repurchases under the program. The Company expects to fund any additional unit repurchases with a combination of available cash balances and availability under its unsecured revolving credit facility. The timing and amounts of any purchases will depend on a variety of factors, including market conditions, regulatory requirements, unit prices, capital availability and other factors as determined by the Company’s management team. The repurchase program does not require the purchase of any minimum number of units and may be suspended or discontinued at any time without notice. The common units repurchased were retired and, as a result, were accounted for in accordance with Maryland law, which does not contemplate treasury stock. The repurchases were recorded as a reduction of common units (at $0.01 par value per unit) and a decrease to General Partnership Capital. Continuous Offering Program On January 10, 2017, the Parent Company entered into a continuous offering program (the “Offering Program”), under which it may sell up to an aggregate of 16,000,000 common units until January 10, 2020 in at-the-market offerings. In connection with the commencement of the Offering Program, $0.2 million of upfront costs were recorded to General Partner Capital. This program is a replacement of a prior continuous offering program that expired on November 3, 2016. During 2018 and 2017, the Parent Company issued 23,311 and 2,858,991 common units under the Offering Program at weighted average prices per unit of $18.04 and $18.19, receiving net cash proceeds of $0.4 million and $51.2 million, respectively. No shares were issued during 2016 under the prior continuous offering program that expired on November 3, 2016. As of December 31, 2018, 13,117,698 common shares remain available for issuance under the Offering Program.

Share Based Compensation, 401(k

Share Based Compensation, 401(k) Plan and Deferred Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
SHARE BASED COMPENSATION, 401(k) PLAN AND DEFERRED COMPENSATION	13. SHARE BASED COMPENSATION, 401(k) PLAN AND DEFERRED COMPENSATION Stock Options On December 31, 2018, options exercisable for 964,359 common shares were outstanding under the Parent Company’s shareholder approved equity incentive plan (referred to as the “Equity Incentive Plan”). During the years ended December 31, 2018, 2017 and 2016, the Company did not recognize any compensation expense related to unvested options. During the years ended December 31, 2018, 2017 and 2016, the Company did not capitalize any compensation expense related to stock options as part of the Company’s review of employee salaries eligible for capitalization. Option activity as of December 31, 2018 and changes during the year-ended December 31, 2018 were as follows: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at January 1, 2018 2,238,590 $ 15.67 1.10 Exercised - $ - $ - Forfeited/Expired (1,274,231 ) $ 20.61 Outstanding at December 31, 2018 964,359 $ 9.13 1.25 $ 3,652,903 Vested/Exercisable at December 31, 2018 964,359 $ 9.13 1.25 $ 3,652,903 401(k) Plan The Company sponsors a 401(k) defined contribution plan for its employees. Each employee may contribute up to 100% of annual compensation, subject to specific limitations under the Internal Revenue Code. At its discretion, the Company can make matching contributions equal to a percentage of the employee’s elective contribution and profit sharing contributions. The Company funds its 401(k) contributions annually and plan participants must be employed as of December 31 st Restricted Share Rights Awards As of December 31, 2018, 466,439 restricted share rights were outstanding under the Equity Incentive Plan and vest over two to three years from the initial grant dates. The remaining compensation expense to be recognized with respect to these awards at December 31, 2018 was approximately $1.8 million and is expected to be recognized over a weighted average remaining vesting period of 1.3 years. For the year ended December 31, 2018, the Company recognized compensation expense related to outstanding restricted shares of $3.6 million, of which $0.6 million was capitalized as part of the Company’s review of employee salaries eligible for capitalization. For the years ended December 31, 2017 and 2016, the Company recognized $2.8 million (of which $0.4 million was capitalized) and $2.6 million (of which $0.4 million was capitalized), respectively, of compensation expense included in general and administrative expense in the respective periods related to outstanding restricted shares. The following table summarizes the Company’s restricted share activity during the year-ended December 31, 2018: Shares Weighted Average Grant Date Fair Value Aggregate Intrinsic Value Non-vested at January 1, 2018 455,643 $ 14.95 $ 8,288,146 Granted 220,241 15.71 - Vested (197,344 ) 15.87 5,923 Forfeited (12,101 ) 15.04 23,292 Non-vested at December 31, 2018 466,439 $ 14.93 $ 70,677 On February 28, 2018, the Compensation Committee of the Parent Company’s Board of Trustees awarded to officers of the Company an aggregate of In addition, on February 28, 2018, the Compensation Committee awarded non-officer employees an aggregate of 44,062 Restricted Share Rights that vest in three equal annual installments on April 15 of 2019, 2020 and 2021. Vesting of these awards is subject to acceleration upon death, disability or termination without cause within one year following a change of control. In accordance with the accounting standard for share-based compensation, the Company amortizes share-based compensation costs through the qualifying retirement dates for those executives who meet the conditions for qualifying retirement during the scheduled vesting period and whose award agreements provide for vesting upon a qualifying retirement. Restricted Performance Share Units Plan The Compensation Committee of the Parent Company’s Board of Trustees has granted performance share-based awards (referred to as Restricted Performance Share Units, or RPSUs) to officers of the Parent Company. The RPSUs are settled in common shares, with the number of common shares issuable in settlement determined based on the Company’s total shareholder return over specified measurement periods compared to total shareholder returns of comparative groups over the measurement periods. The table below presents certain information as to unvested RPSU awards. RPSU Grant 2/22/2016 3/1/2017 2/28/2018 Total (Amounts below in shares, unless otherwise noted) Non-vested at January 1, 2018 228,077 172,411 - 400,488 Units Granted - - 209,193 209,193 Units Cancelled (3,354 ) (2,886 ) (3,168 ) (9,408 ) Non-vested at December 31, 2018 224,723 169,525 206,025 600,273 Measurement Period Commencement Date 1/1/2016 1/1/2017 1/1/2018 Measurement Period End Date 12/31/2018 12/31/2019 12/31/2020 Units Granted 231,388 174,854 209,193 Fair Value of Units on Grant Date (in thousands) $ 3,558 $ 3,735 $ 4,276 The Company values each RPSU on its grant date using a Monte Carlo simulation. The fair values of each award are being amortized over the three year cliff vesting period. The vesting of RPSUs is subject to acceleration upon a change in control or if the recipient of the award were to die, become disabled or retire in a qualifying retirement prior to the vesting date. In accordance with the accounting standard for share-based compensation, the Company amortizes stock-based compensation costs through the qualifying retirement date for those executives who meet the conditions for qualifying retirement during the scheduled vesting period. For the year ended December 31, 2018, the Company recognized total compensation expense for the 2018, 2017 and 2016 RPSU awards of $3.9 million, of which $1.1 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. For the year ended December 31, 2017, the Company recognized total compensation expense for the 2017, 2016 and 2015 RPSU awards of $3.4 million, of which $0.8 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. For the year ended December 31, 2016, the Company recognized total compensation expense for the 2016, 2015 and 2014 RPSU awards of $2.8 million, of which $0.6 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. The remaining compensation expense to be recognized at December 31, 2018 was approximately $2.0 million and is expected to be recognized over a weighted average remaining vesting period of 1.1 years. The Company issued 193,516 common shares on February 1, 2018 in settlement of RPSUs that had been awarded on February 23, 2015 (with a three-year measurement period ended December 31, 2017). Holders of these RPSUs also received a cash dividend of $0.18 per share for these common shares on February 9, 2018. Employee Share Purchase Plan The Parent Company’s shareholders approved the 2007 Non-Qualified Employee Share Purchase Plan (the “ESPP”), which is intended to provide eligible employees with a convenient means to purchase common shares of the Parent Company through payroll deductions and voluntary cash purchases at an amount equal to 85% of the average closing price per share for a specified period. Under the plan document, the maximum participant contribution for the 2018 plan year is limited to the lesser of 20% of compensation or $50,000. The ESPP allows the Parent Company to make open market purchases, which reflects all purchases made under the plan to date. In addition, the number of shares separately reserved for issuance under the ESPP is 1.25 million. During the year ended December 31, 2018, employees made purchases under the ESPP of $0.5 million and the Company recognized $0.1 million of compensation expense related to the ESPP. During each of the years ended December 31, 2017 and 2016, employees made purchases under the ESPP of $0.4 million. For the years ended December 31, 2017 and 2016, the Company recognized $0.1 million and $0.2 million of compensation expense related to the ESPP, respectively. Compensation expense represents the 15% discount on the purchase price. The Board of Trustees of the Parent Company may terminate the ESPP at its sole discretion at any time. Deferred Compensation In January 2005, the Parent Company adopted a Deferred Compensation Plan (the “Plan”) that allows trustees and certain key employees to defer compensation voluntarily. Compensation expense is recorded for the deferred compensation and a related liability is recognized. Participants may elect designated benchmark investment options for the notional investment of their deferred compensation. The deferred compensation obligation is adjusted for deemed income or loss related to the investments selected. At the time the participants defer compensation, the Company records a liability, which is included in the Company’s consolidated balance sheets. The liability is adjusted for changes in the market value of the participant-selected investments at the end of each accounting period, and the impact of adjusting the liability is recorded as an increase or decrease to compensation cost. The Company has purchased mutual funds which can be utilized as a funding source for the Company’s obligations under the Plan. Participants in the Plan have no interest in any assets set aside by the Company to meet its obligations under the Plan. For each of the years ended December 31, 2018, December 31, 2017 and December 31, 2016, the Company recorded a nominal amount of deferred compensation costs, net of investments in the company-owned policies and mutual funds. Participants in the Plan may elect to have all or a portion of their deferred compensation invested in the Company’s common shares. The Company holds these shares in a rabbi trust, which is subject to the claims of the Company’s creditors in the event of the Company’s bankruptcy or insolvency. The Plan does not permit diversification of a participant’s deferral allocated to the Company common shares and deferrals allocated to Company common shares can only be settled with a fixed number of shares. In accordance with the accounting standard for deferred compensation arrangements where amounts earned are held in a rabbi trust and invested, the deferred compensation obligation associated with the Company’s common shares is classified as a component of shareholder’s equity and the related shares are treated as shares to be issued and are included in total shares outstanding. At December 31, 2018 and 2017, 1.0 million and 0.9 million of such shares were included in total shares outstanding, respectively. Subsequent changes in the fair value of the common shares are not reflected in operations or shareholders’ equity of the Company.

Distributions

Distributions	12 Months Ended
	Dec. 31, 2018
Distributions [Abstract]
DISTRIBUTIONS	14. DISTRIBUTIONS The following table provides the tax characteristics of the 2018, 2017 and 2016 distributions paid: Years ended December 31, 2018 2017 2016 (in thousands, except per share amounts) Common Share Distributions: Ordinary income $ 0.55 $ 0.38 $ - Capital gain - 0.26 0.62 Non-taxable distributions 0.17 - - Distributions per share $ 0.72 $ 0.64 $ 0.62 Percentage classified as ordinary income 76.20 % 60.00 % 0.00 % Percentage classified as capital gain 0.00 % 40.00 % 100.00 % Percentage classified as non-taxable distribution 23.80 % 0.00 % 0.00 % Preferred Share Distributions: Total distributions paid $ - $ 2,032 $ 6,900 Percentage classified as ordinary income 0.00 % 60.00 % 0.00 % Percentage classified as capital gain 0.00 % 40.00 % 100.00 % Percentage classified as non-taxable distribution 0.00 % 0.00 % 0.00 %

Income Taxes and Tax Credit Tra

Income Taxes and Tax Credit Transactions	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES AND TAX CREDIT TRANSACTIONS	15. INCOME TAXES AND TAX CREDIT TRANSACTIONS Income Tax Provision/Benefit The Company accounts for income taxes using the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective income tax bases, and for net operating loss, capital loss and tax credit carryforwards. The deferred tax assets and liabilities are measured using the enacted income tax rates in effect for the year in which those temporary differences are expected to be realized or settled. The effect on the deferred tax assets and liabilities from a change in tax rates is recognized in earnings in the period when the new rate is enacted. However, deferred tax assets are recognized only to the extent that it is more likely than not that they will be realized based on consideration of all available evidence, including the future reversals of existing taxable temporary differences, future projected taxable income and tax planning strategies. Valuation allowances are provided if, based upon the weight of the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. As of December 31, 2018, net deferred tax assets totaled $0.1 million and are included in the “Other assets” caption within the Company’s consolidated balance sheets. There were $0.6 million of net deferred tax assets at December 31, 2017 included in the “Other assets” caption within the Company’s consolidated balance sheets. In projecting future taxable income, the analysis begins with historical results and incorporates assumptions about the amount of future state and federal pretax operating income adjusted for items that do not have tax consequences. The assumptions about future taxable income require significant judgment and are consistent with the plans and estimates the Company is using to manage the underlying businesses. The Company had no accruals for tax uncertainties as of December 31, 2018 and December 31, 2017. For the year ended December 31, 2018, there were $0.3 million of deferred income tax expense and $0.1 million of current income tax expense. For the year ended December 31, 2017, there were $0.6 million of deferred income tax benefits. For the year ended December 31, 2016, there was a nominal amount of income tax expense. These amounts are included in the “Income tax (provision) benefit” caption in the Company’s consolidated statements of operations for each respective year ended.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2018
Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	16. ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The following table details the components of accumulated other comprehensive income (loss) of the Parent Company and the Operating Partnership as of and for the three years ended December 31, 2018 (in thousands): Parent Company Cash Flow Hedges Balance at January 1, 2016 $ (5,192 ) Change in fair market value during year 2,371 Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests (28 ) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,104 Balance at December 31, 2016 $ (1,745 ) Change in fair market value during year 2,948 Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests (34 ) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,230 Balance at December 31, 2017 $ 2,399 Change in fair market value during year 1,478 Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests (39 ) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,191 Balance at December 31, 2018 $ 5,029 Operating Partnership Cash Flow Hedges Balance at January 1, 2016 $ (5,597 ) Change in fair market value during year 2,371 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,104 Balance at December 31, 2016 $ (2,122 ) Change in fair market value during year 2,948 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,230 Balance at December 31, 2017 $ 2,056 Change in fair market value during year 1,478 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,191 Balance at December 31, 2018 $ 4,725 Over time, the unrealized gains and losses held in Accumulated Other Comprehensive Income (“AOCI”) will be reclassified to interest expense when the related hedged items are recognized in earnings. The current balance held in AOCI is expected to be reclassified to interest expense for realized losses on forecasted debt transactions over the related term of the debt obligation, as applicable. The Company expects to reclassify $0.8 million from AOCI into interest expense within the next twelve months.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
SEGMENT INFORMATION	17. SEGMENT INFORMATION During the year ended December 31, 2018, the Company owned and managed its portfolio within five segments: (1) Philadelphia Central Business District (Philadelphia CBD), (2) Pennsylvania Suburbs, (3) Austin, Texas (4) Metropolitan Washington, D.C., and (5) Other. The Philadelphia CBD segment includes properties located in the City of Philadelphia, Pennsylvania. The Pennsylvania Suburbs segment includes properties in Chester, Delaware, and Montgomery counties in the Philadelphia suburbs. The Austin, Texas segment includes properties in the City of Austin, Texas. The Metropolitan Washington, D.C. segment includes properties in the District of Columbia, Northern Virginia and southern Maryland. The Other segment includes properties located in Camden County in New Jersey and properties in New Castle County in Delaware. In addition to the five segments, the corporate group is responsible for cash and investment management, development of certain real estate properties during the construction period, and certain other general support functions. Land held for development and construction in progress is transferred to operating properties by region upon completion of the associated construction or project. The following tables provide selected asset information and results of operations of the Company’s reportable segments for the three years ended December 31, 2018, 2017 and 2016 (in thousands): Real estate investments, at cost: December 31, 2018 December 31, 2017 December 31, 2016 Philadelphia CBD $ 1,670,388 $ 1,643,296 $ 1,320,974 Pennsylvania Suburbs 1,004,537 958,796 1,005,446 Metropolitan Washington, D.C. (a) 524,190 978,257 975,987 Austin, Texas (b) 667,698 163,653 146,794 Other 86,506 88,346 137,094 $ 3,953,319 $ 3,832,348 $ 3,586,295 Assets held for sale (c) - - 73,591 Operating Properties $ 3,953,319 $ 3,832,348 $ 3,659,886 Corporate Construction-in-progress $ 150,263 $ 121,188 $ 297,462 Land held for development (d) $ 86,401 $ 98,242 $ 150,970 Prepaid leasehold interests in land held for development, net $ 39,999 $ - $ - (a) On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment, known as the Rockpoint Portfolio, to the Herndon Innovation Center Metro Portfolio Venture, LLC for a gross sales price of $312.0 million. The Company and its partner own 15% and 85% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. The Herndon Innovation Center Metro Portfolio Venture, LLC funded the acquisition with $265.2 million of cash, which was distributed to the Company at closing. After funding its share of closing costs and working capital contributions of $2.2 million and $0.6 million, respectively, the Company received $262.4 million of cash proceeds at settlement. For further information related to this transaction, see the “ Herndon Innovation Center Metro Portfolio Venture, LLC Investment in Unconsolidated Real Estate Ventures (b) On December 11, 2018, the Company acquired from DRA Advisors its 50% ownership interest in the G&I Austin Office LLC real estate venture for an aggregate purchase price of $535.1 million. The DRA Austin Venture owned twelve office properties containing an aggregate 1,570,123 square feet, located in Austin, Texas. As a result of the acquisition, the Company acquired complete ownership of the Austin Venture Portfolio. For further information related to this transaction, see the “ Acquisitions” Real Estate Investments (c) As of December 31, 2016, three office properties in the Metropolitan Washington, D.C. segment and two office properties in the Other segment were classified as held for sale in accordance with applicable accounting standards for long-lived assets. See the “ 2016 ” section of Note 3, “Real Estate Investments,” for further information. (d) As of December 31, 2018, the Company classified 37.9 acres of land held for development , comprised of 2.7 acres and 35.2 acres, located in its Pennsylvania Suburbs segment and Other segment, respectively, as held for sale in accordance with applicable accounting standards for long lived assets. See Note 3 , “Real Estate Investments,” for further information. As of December 31, 2017, the Company classified 13.1 acres of land held for development located in its Other segment as held for sale in accordance with applicable accounting standards for long lived assets. (e) As of December 31, 2018, this caption comprised leasehold interests in prepaid 99-year ground leases at 3025 and 3001-3003 JFK Boulevard, in Philadelphia, Pennsylvania. See Note 3, “Real Estate Investments None of the above aforementioned sales or properties classified as held for sale are considered significant dispositions under the accounting guidance for discontinued operations. Years ended December 31, 2018 2017 2016 Total revenue Operating expenses (a) Net operating income (loss) Total revenue Operating expenses (a) Net operating income Total revenue Operating expenses (a) Net operating income Philadelphia CBD $ 256,717 $ (99,449 ) $ 157,268 $ 226,673 $ (88,818 ) $ 137,855 $ 200,245 $ (78,708 ) $ 121,537 Pennsylvania 138,279 (49,357 ) 88,922 139,785 (47,769 ) 92,016 144,338 (49,208 ) 95,130 Metropolitan 90,308 (34,072 ) 56,236 92,024 (35,014 ) 57,010 99,781 (39,036 ) 60,745 Austin, Texas 38,665 (16,739 ) 21,926 34,301 (15,456 ) 18,845 34,585 (13,222 ) 21,363 Other 16,757 (11,888 ) 4,869 18,347 (11,749 ) 6,598 39,359 (23,204 ) 16,155 Corporate 3,619 (6,518 ) (2,899 ) 9,363 (7,193 ) 2,170 7,155 (6,070 ) 1,085 Operating $ 544,345 $ (218,023 ) $ 326,322 $ 520,493 $ (205,999 ) $ 314,494 $ 525,463 $ (209,448 ) $ 316,015 (a) Includes property operating expense, real estate taxes and third party management expense. Unconsolidated real estate ventures: Investment in real estate ventures, at equity Equity in income (loss) of real estate venture As of Years ended December 31, December 31, 2018 December 31, 2017 December 31, 2016 2018 2017 2016 Philadelphia CBD $ 19,897 $ 39,939 $ 48,691 $ (105 ) $ 255 $ (686 ) Pennsylvania Suburbs - 3,503 15,421 - 631 748 Metropolitan Washington, D.C. (a) 136,142 119,817 141,786 (15,065 ) (5,044 ) (6,293 ) MAP Venture (b) 11,173 15,450 20,893 (2,155 ) (3,443 ) (4,218 ) Other 1,888 1,939 1,654 407 285 814 Austin, Texas (c) - 13,973 52,886 1,687 (990 ) (1,868 ) Total $ 169,100 $ 194,621 $ 281,331 $ (15,231 ) $ (8,306 ) $ (11,503 ) (a) On December 20, 2018, the Company formed a joint venture with Rockpoint. See footnote (a) to the “Real estate investments, at cost” (b) The MAP Venture represents a joint venture formed between the Company and MAP Ground Lease Holdings LLC, an affiliate of Och-Ziff Capital Management Group, LLC, on February 4, 2016. The MAP Venture’s business operations, including properties in Richmond, Virginia; Metropolitan Washington, D.C.; New Jersey/Delaware and Pennsylvania Suburbs, are centrally managed with the results reported to management of the Company on a consolidated basis. As a result, the investment in the MAP Venture is separately presented. All other unconsolidated real estate ventures are managed consistently with the Company’s regional segments. (c) See footnote (b) to the “Real estate investments, at cost” table above for further information regarding this transaction. Net operating income (“NOI”) is a non-GAAP financial measure defined as total revenue less property operating expenses, real estate taxes and third party management expenses. Property operating expenses that are included in determining NOI consist of costs that are necessary and allocable to our operating properties such as utilities, property-level salaries, repairs and maintenance, property insurance, management fees and bad debt expense. General and administrative expenses that are not reflected in NOI primarily consist of corporate-level salaries, amortization of share awards and professional fees that are incurred as part of corporate office management. All companies may not calculate NOI in the same manner. NOI is the measure that is used by the Company to evaluate the operating performance of its real estate assets by segment. The Company believes NOI provides useful information to investors regarding the financial condition and results of operations because it reflects only those income and expense items that are incurred at the property level. While NOI is a relevant and widely used measure of operating performance of real estate investment trusts, it does not represent cash flow from operations or net income as defined by GAAP and should not be considered as an alternative to those measures in evaluating our liquidity or operating performance. NOI does not reflect interest expenses, real estate impairment losses, depreciation and amortization costs, capital expenditures and leasing costs. The Company believes that net income (loss), as defined by GAAP, is the most appropriate earnings measure. The following is a reconciliation of consolidated net income (loss), as defined by GAAP, to consolidated NOI, (in thousands): Years Ended December 31, 2018 2017 2016 Net income $ 137,289 $ 121,859 $ 40,501 Plus: Interest expense 78,199 81,886 84,708 Interest 2,498 2,435 2,696 Interest expense - financing obligation - - 679 Depreciation and amortization 174,259 179,357 189,676 General and administrative expenses 27,802 28,538 26,596 Equity in loss of Real Estate Ventures 15,231 8,306 11,503 Provision for impairment 71,707 3,057 40,517 Loss on early extinguishment of debt 105 3,933 66,590 Less: Interest income 4,703 1,113 1,236 Income tax (provision) benefit (423 ) 628 - Net gain on disposition of real estate 2,932 31,657 116,983 Net gain on sale of undepreciated real estate 3,040 953 9,232 Net gain on real estate venture transactions 142,233 80,526 20,000 Gain on promoted interest in unconsolidated real estate venture 28,283 - - Consolidated net operating income $ 326,322 $ 314,494 $ 316,015

Operating Leases

Operating Leases	12 Months Ended
	Dec. 31, 2018
Leases Operating [Abstract]
OPERATING LEASES	18. OPERATING LEASES The Company leases properties to tenants under operating leases with various expiration dates extending to 2082. Minimum future rentals on non-cancelable leases at December 31, 2018 are as follows (in thousands): Year Minimum Rent 2019 $ 392,058 2020 372,619 2021 349,160 2022 304,445 2023 277,388 Thereafter 1,265,810 Total minimum future rentals presented above do not include amounts to be received as tenant reimbursements for operating costs.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	19. COMMITMENTS AND CONTINGENCIES Legal Proceedings The Company is involved from time to time in litigation on various matters, including disputes with tenants, disputes with vendors, employee disputes and disputes arising out of agreements to purchase or sell properties or joint ventures or disputes relating to state and local taxes. Given the nature of the Company’s business activities, these lawsuits are considered routine to the conduct of its business. The result of any particular lawsuit cannot be predicted, because of the very nature of litigation, the litigation process and its adversarial nature, and the jury system. The Company will establish reserves for specific legal proceedings when it determines that the likelihood of an unfavorable outcome is probable and when the amount of loss is reasonably estimable. The Company does not expect that the liabilities, if any, that may ultimately result from such legal actions will have a material adverse effect on the consolidated financial position, results of operations or cash flows of the Company. Letters-of-Credit Under certain mortgages, the Company has funded required leasing and capital reserve accounts for the benefit of the mortgage lenders with letters-of-credit. There were no associated letters-of-credit for a mortgage lender on December 31, 2018. Certain of the tenant rents at properties that secure these mortgage loans are deposited into the loan servicer’s depository accounts, which are used to fund debt service, operating expenses, capital expenditures and the escrow and reserve accounts, as necessary. Any excess cash is included in cash and cash equivalents. Environmental As an owner of real estate, the Company is subject to various environmental laws of federal, state, and local governments. The Company’s compliance with existing laws has not had a material adverse effect on its financial condition and results of operations, and the Company does not believe it will have a material adverse effect in the future. However, the Company cannot predict the impact of unforeseen environmental contingencies or new or changed laws or regulations on its current Properties or on properties that the Company may acquire. Ground Rent Future minimum rental payments under the terms of all non-cancellable ground leases under which the Company is the lessee are expensed on a straight-line basis regardless of when payments are due. The Company’s ground leases have remaining lease terms ranging from 10 to 66 years. Minimum future rental payments on non-cancelable leases at December 31, 2018 are as follows (in thousands): Year Minimum Rent 2019 $ 1,222 2020 1,222 2021 1,222 2022 1,222 2023 1,222 Thereafter 55,689 Total $ 61,799 The Company obtained ground tenancy rights related to three properties in Philadelphia, Pennsylvania, which provide for contingent rent participation by the lessor in certain capital transactions and net operating cash flows of the properties after certain returns are achieved by the Company. Such amounts, if any, will be reflected as contingent rent when incurred. The leases also provide for payment by the Company of certain operating costs relating to the land, primarily real estate taxes. The above schedule of future minimum rental payments does not include any contingent rent amounts or any reimbursed expenses. Fair Value of Contingent Consideration On April 2, 2015, the Company purchased 618 Market Street in Philadelphia, Pennsylvania. The allocated purchase price included contingent consideration of $2.0 million payable to the seller upon commencement of development. The liability was recorded at a fair value of $1.6 million and will accrete through interest expense to $2.0 million over the expected period until development is commenced. The fair value of this contingent consideration was determined using a probability weighted discounted cash flow model. The significant inputs to the discounted cash flow model were the discount rate and weighted probability scenarios. As the inputs are unobservable, the Company determined the inputs used to value this liability fall within Level 3 for fair value reporting. As of December 31, 2018, the liability had accreted to $1.9 million. As there were no significant changes to the inputs, the liability remains within Level 3 for fair value reporting. Debt Guarantees As of December 31, 2018, the Company’s unconsolidated real estate ventures had aggregate indebtedness of $370.3 million. These loans are generally mortgage or construction loans, most of which are non-recourse to the Company, except for customary carve-outs. As of December 31, 2018, the loans for which there is recourse to the Company consist of the following: (i) a $0.3 million payment guarantee on a loan with a $3.8 million outstanding principal balance, provided to PJP VII and (ii) up to a $41.3 million payment guarantee on a $150.0 million construction loan provided to 4040 Wilson. In addition, during construction undertaken by real estate ventures, including 4040 Wilson, the Company has provided and expects to continue to provide cost overrun and completion guarantees, with rights of contribution among partners or members in the real estate ventures, as well as customary environmental indemnities and guarantees of customary exceptions to nonrecourse provisions in loan agreements. Other Commitments or Contingencies On October 13, 2017, the Company acquired a leasehold interest in the office building known as The Bulletin Building, in Philadelphia, Pennsylvania. See Note 3, “Real Estate Investments,” for further information. In connection with the acquisition, the Company is required to spend no less than $8.0 million in capital improvements to the property. As of December 31, 2018, $1.2 million of the funding related to this requirement had been met. The Company estimates that it will incur $37.3 million in excess of this funding requirement and expects to complete the redevelopment of The Bulletin Building during the second quarter of 2020 at an estimated aggregate cost of $83.1 million, inclusive of the acquisition cost of $37.8 million. Also on October 13, 2017, the Company acquired a leasehold interest in the land parcel at 3001 Market Street in Philadelphia, Pennsylvania (“Drexel Square”). During the fourth quarter of 2017, the Company broke ground on the construction of a public park on the site, marking the commencement of construction of its Schuylkill Yards Project with Drexel. Under the terms of the Development Agreement with Drexel, the Company has until July 2019 to complete development of Drexel Square. If the Company is unable to complete such development within this timeframe, it may be subject to damages under the Development Agreement. As of December 31, 2018, the project is substantially complete. During the fourth quarter of 2017, in connection with the Schuylkill Yards Project, the Company entered into a neighborhood engagement program and, as of December 31, 2018, had $2.7 million of future contractual obligations. In addition, the Company estimates $0.6 million of potential additional contributions for which the Company is not currently contractually obligated. As part of the Company’s September 2004 acquisition of a portfolio of properties from The Rubenstein Company (which the Company refers to as the “TRC acquisition”), the Company acquired its interest in Two Logan Square, a 708,844 square foot office building in Philadelphia, primarily through its ownership of a second and third mortgage secured by this property. This property is consolidated, as the borrower is a variable interest entity and the Company, through its ownership of the second and third mortgages, is the primary beneficiary. The Company currently does not expect to take title to Two Logan Square until, at the earliest, on or about August 2020. If the Company takes fee title to Two Logan Square upon foreclosure of its mortgage, the Company has agreed to pay an unaffiliated third party that holds a residual interest in the fee owner of this property an amount equal to $2.9 million. On the TRC acquisition date, the Company recorded a liability of $0.7 million and this amount will accrete up to $2.9 million through January 2020. As of December 31, 2018, the Company had a balance of $2.7 million for this liability in its consolidated balance sheets. As part of the Company’s 2006 merger with Prentiss Properties Trust (“Prentiss”), the 2004 TRC acquisition and several of our other transactions, the Company agreed not to sell certain of the properties it acquired in transactions that would trigger taxable income to the former owners. In the case of the TRC acquisition, the Company agreed not to sell acquired properties in non-exempt transactions for periods up to 15 years from the date of the TRC acquisition as follows at December 31, 2018: One Logan Square, Two Logan Square and Radnor Corporate Center (January 2020). The Company subsequently agreed to extend the no-sale period applicable to Two Logan Square to on or about August 2020. In the Prentiss acquisition, the Company assumed the obligation of Prentiss not to sell Concord Airport Plaza before March 2018. The Company’s agreements generally provide that it may dispose of the subject properties only in transactions that qualify as tax-free exchanges under Section 1031 of the Internal Revenue Code or in other tax deferred transactions. On February 2, 2017, the Company completed the disposition of Concord Airport Plaza in a transaction that qualified as a tax-free exchange under Section 1031 of the Internal Revenue Code. See Note 3, “Real Estate Investments,” for further information. If the Company were to sell a restricted property before the expiration of the restricted period in a non-exempt transaction, the Company may be required to make significant payments to the parties who sold the applicable property on account of tax liabilities attributed to them. Similarly, as part of the 2013 acquisition of substantially all of the equity interests in the partnerships that own One and Two Commerce Square, the Company agreed, for the benefit of affiliates of the holder of the 1 % residual ownership interest in these properties, to not sell these two properties in certain taxable transactions prior to October 20, 2021 without the holder’s consent. As part of the Company’s acquisition of properties from time to time in tax-deferred transactions, the Company has agreed to provide certain of the prior owners of the acquired properties with the right to guarantee the Company’s indebtedness. If the Company were to seek to repay the indebtedness guaranteed by the prior owner before the expiration of the applicable agreement, the Company would be required to provide the prior owner an opportunity to guaranty qualifying replacement debt. These debt maintenance agreements may limit the Company’s ability to refinance indebtedness on terms favorable to the Company. As part of our 2013 acquisition of substantially all of the equity interests in the partnerships that own One and Two Commerce Square, the Company agreed, for the benefit of affiliates of the holder of the 1% residual ownership interest in these properties, to maintain qualifying mortgage debt through October 20, 2021, in the amounts of not less than $125.0 million on One Commerce Square and $100.0 million on Two Commerce Square. Similarly, the Company has agreements in place with other contributors of assets that obligate it to maintain debt available for them to guaranty. The Company invests in its properties and regularly incurs capital expenditures in the ordinary course of business to maintain the properties. The Company believes that such expenditures enhance its competitiveness. The Company also enters into construction, utility and service contracts in the ordinary course of business which may extend beyond one year. These contracts typically provide for cancellation with insignificant or no cancellation penalties.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	20. SUBSEQUENT EVENTS On January 3, 2019, the Board of Trustees authorized the repurchase of up to $150.0 million common shares from and after January 3, 2019. During January 2019, the Company repurchased and retired 1,337,169 common shares at an average price of $12.92 per share, totaling $17.3 million.

Summary of Quarterly Results

Summary of Quarterly Results	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
SUMMARY OF QUARTERLY RESULTS (UNAUDITED)	21. SUMMARY OF QUARTERLY RESULTS (UNAUDITED) The following is a summary of quarterly financial information as of and for the years ended December 31, 2018 and 2017 (in thousands, except per share data): Brandywine Realty Trust 1st 2nd 3rd 4th Quarter Quarter Quarter Quarter 2018 Total revenue $ 136,358 $ 133,786 $ 134,998 $ 139,203 (b) Net income (loss) 44,705 13,136 (43,262 ) (a) 122,710 (c) Net income (loss) allocated to Common Shares 44,215 12,920 (43,003 ) 121,823 Basic earnings (loss) per Common Share $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 Diluted earnings (loss) per Common Share $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 2017 Total revenue $ 130,920 $ 127,791 $ 128,438 $ 133,344 Net income 21,271 7,698 19,046 73,844 Net income allocated to Common Shares 19,278 4,092 18,803 73,137 Basic earnings per Common Share $ 0.11 $ 0.02 $ 0.11 $ 0.42 Diluted earnings per Common Share $ 0.11 $ 0.02 $ 0.11 $ 0.41 The summation of quarterly earnings per share amounts does not necessarily equal the full year amounts due to rounding. (a) The decrease in third quarter net income primarily relates to a $56.9 million impairment charge which related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, “Real Estate Investments,” (b) The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, “Real Estate Investments,” for further information on this transaction. (c) The increase in net income for the fourth quarter primarily relates to gains of $103.8 million and $28.3 million, recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, "Real Estate Investments." Brandywine Operating Partnership, L.P. 1st 2nd 3rd 4th Quarter Quarter Quarter Quarter 2018 Total revenue $ 136,358 $ 133,786 $ 134,998 $ 139,203 (b) Net income (loss) 44,705 13,136 (43,262 ) (a) 122,710 (c) Net income (loss) attributable to Common Partnership Unitholders 44,586 13,029 (43,362 ) 122,612 Basic earnings (loss) per Common Partnership Unit $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 Diluted earnings (loss) per Common Partnership Unit $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 2017 Total revenue $ 130,920 $ 127,791 $ 128,438 $ 133,344 Net income 21,271 7,698 19,046 73,844 Net income attributable to Common Partnership Unitholders 19,442 4,129 18,961 73,758 Basic earnings per Common Partnership Unit $ 0.11 $ 0.02 $ 0.11 $ 0.42 Diluted earnings per Common Partnership Unit $ 0.11 $ 0.02 $ 0.11 $ 0.41 The summation of quarterly earnings per share amounts does not necessarily equal the full year amounts due to rounding. (a) (a)The decrease in third quarter net income primarily relates to a $56.9 million impairment charge which related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, “Real Estate Investments,” (b) The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, “Real Estate Investments,” (c) The increase in net income for the fourth quarter primarily relates to gains of $103.8 million and $28.3 million, recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, "Real Estate Investments."

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2018
Valuation And Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure	Brandywine Realty Trust and Brandywine Operating Partnership, L.P. Schedule II Valuation and Qualifying Accounts (in thousands) Description Balance at Beginning of Year Additions Deductions (1) Balance at End of Year Allowance for doubtful accounts: Year-ended December 31, 2018 $ 17,112 $ 1,775 $ 5,968 $ 12,919 Year-ended December 31, 2017 $ 16,116 $ 1,912 $ 916 $ 17,112 Year-ended December 31, 2016 $ 16,178 $ 2,207 $ 2,269 $ 16,116 (1) Deductions represent amounts that the Company had fully reserved for in prior years and for which the pursuit of collection of such amounts was ceased during the year.

Schedule III - Real Estate and

Schedule III - Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2018
Real Estate And Accumulated Depreciation Disclosure [Abstract]
Real Estate and Accumulated Depreciation Disclosure	BRANDYWINE REALTY TRUST AND BRANDYWINE OPERATING PARTNERSHIP, L.P. Schedule III Real Estate and Accumulated Depreciation — December 31, 2018 (in thousands) Initial Cost Gross Amount Which Carried December 31, 2018 Property Name City State Encumbrances (a) Land Building & Improvements Net Improvements (Retirements) Since Acquisition Land Building & Improvements Total (b) Accumulated Depreciation at December 31, 2018 (c) Year of Construction Year Acquired Depreciable Life PENNSYLVANIA SUBURBS 400 Berwyn Park Berwyn PA - 2,657 4,462 12,985 2,657 $ 17,447 20,104.00 8,060 1999 1999 40 300 Berwyn Park Berwyn PA - 2,206 13,422 3,331 2,206 $ 16,753 18,959.00 9,777 1989 1997 40 1050 Westlakes Drive Berwyn PA - 2,611 10,445 2,416 2,611 $ 12,861 15,472.00 5,990 1984 1999 40 1200 Swedesford Road Berwyn PA - 2,595 11,809 218 2,595 $ 12,027 14,622.00 6,211 1994 2001 40 200 Berwyn Park Berwyn PA - 1,533 9,460 2,074 1,533 $ 11,534 13,067.00 6,586 1987 1997 40 1180 Swedesford Road Berwyn PA - 2,086 8,342 3,110 2,086 $ 11,452 13,538.00 5,496 1987 2001 40 100 Berwyn Park Berwyn PA - 1,180 7,290 1,636 1,180 $ 8,926 10,106.00 5,012 1986 1997 40 1160 Swedesford Road Berwyn PA - 1,781 7,124 6,831 2,045 $ 13,691 15,736.00 5,864 1986 2001 40 1100 Cassett Road Berwyn PA - 1,695 6,779 1,662 1,695 $ 8,441 10,136.00 3,714 1997 2001 40 Six Tower Bridge (181 Washington Street) Conshohocken PA - 6,927 14,722 2,448 6,237 $ 17,860 24,097.00 2,920 1999 2013 40 52 Swedesford Square East Whiteland Twp. PA - 4,241 16,579 5,418 4,241 $ 21,997 26,238.00 10,712 1988 1998 40 640 Freedom Business Center King Of Prussia PA - 4,222 16,891 4,827 4,222 $ 21,718 25,940.00 11,254 1991 1998 40 620 Freedom Business Center King Of Prussia PA - 2,770 11,014 2,147 2,770 $ 13,161 15,931.00 6,925 1986 1998 40 1000 First Avenue King Of Prussia PA - 2,772 10,936 3,660 2,772 $ 14,596 17,368.00 7,255 1980 1998 40 1060 First Avenue King Of Prussia PA - 2,712 10,953 3,539 2,712 $ 14,492 17,204.00 7,111 1987 1998 40 630 Freedom Business Center Drive King Of Prussia PA - 2,773 11,144 3,592 2,773 $ 14,736 17,509.00 7,517 1989 1998 40 1020 First Avenue King Of Prussia PA - 2,168 8,576 3,939 2,168 $ 12,515 14,683.00 6,004 1984 1998 40 1040 First Avenue King Of Prussia PA - 2,860 11,282 5,037 2,860 $ 16,319 19,179.00 7,941 1985 1998 40 610 Freedom Business Center Drive King Of Prussia PA - 2,017 8,070 2,547 2,017 $ 10,617 12,634.00 5,319 1985 1998 40 650 Park Avenue King Of Prussia PA - 1,916 4,378 1,357 1,916 $ 5,735 7,651.00 3,418 1968 1998 40 600 Park Avenue King Of Prussia PA - 1,012 4,048 385 1,012 $ 4,433 5,445.00 2,527 1964 1998 40 933 First Avenue King Of Prussia PA - 3,127 20,794 (1,125 ) 3,127 $ 19,669 22,796.00 1,345 2017 N/A 40 500 North Gulph Road King Of Prussia PA - 1,303 5,201 18,777 1,303 $ 23,978 25,281.00 82 1979 1996 401 Plymouth Road Plymouth Meeting PA - 6,199 16,131 16,184 6,199 $ 32,315 38,514.00 14,477 2001 2000 40 Metroplex (4000 Chemical Road) Plymouth Meeting PA - 4,373 24,546 452 4,373 $ 24,998 29,371.00 6,941 2007 2001 40 610 West Germantown Pike Plymouth Meeting PA - 3,651 14,514 3,313 3,651 $ 17,827 21,478.00 7,996 1987 2002 40 600 West Germantown Pike Plymouth Meeting PA - 3,652 15,288 2,377 3,652 $ 17,665 21,317.00 7,422 1986 2002 40 630 West Germantown Pike Plymouth Meeting PA - 3,558 14,743 2,522 3,558 $ 17,265 20,823.00 7,157 1988 2002 40 620 West Germantown Pike Plymouth Meeting PA - 3,572 14,435 1,561 3,572 $ 15,996 19,568.00 6,517 1990 2002 40 660 West Germantown Pike Plymouth Meeting PA - 3,694 5,487 20,715 5,405 $ 24,491 29,896.00 5,636 1987 2012 30 351 Plymouth Road Plymouth Meeting PA - 1,043 555 - 1,043 $ 555 1,598.00 191 N/A 2000 40 150 Radnor Chester Road Radnor PA - 11,925 36,986 9,273 11,897 $ 46,287 58,184.00 20,332 1983 2004 29 One Radnor Corporate Center Radnor PA - 7,323 28,613 23,155 7,323 $ 51,768 59,091.00 28,913 1998 2004 29 201 King of Prussia Road Radnor PA - 8,956 29,811 3,064 8,949 $ 32,882 41,831.00 18,605 2001 2004 25 555 Lancaster Avenue Radnor PA - 8,014 16,508 19,201 8,609 $ 35,114 43,723.00 16,532 1973 2004 24 Four Radnor Corporate Center Radnor PA - 5,406 21,390 12,918 5,705 $ 34,009 39,714.00 14,908 1995 2004 30 Five Radnor Corporate Center Radnor PA - 6,506 25,525 5,887 6,578 $ 31,340 37,918.00 11,579 1998 2004 38 Three Radnor Corporate Center Radnor PA - 4,773 17,961 1,372 4,791 $ 19,315 24,106.00 9,731 1998 2004 29 Two Radnor Corporate Center Radnor PA - 3,937 15,484 3,402 3,942 $ 18,881 22,823.00 9,359 1998 2004 29 130 Radnor Chester Road Radnor PA - 2,573 8,338 3,188 2,567 $ 11,532 14,099.00 6,206 1983 2004 25 170 Radnor Chester Road Radnor PA - 2,514 8,147 2,165 2,509 $ 10,317 12,826.00 4,210 1983 2004 25 200 Radnor Chester Road Radnor PA - 3,366 - 3,572 3,366 $ 3,572 6,938.00 636 2014 2005 40 101 West Elm Street W. Conshohocken PA - 6,251 25,209 3,633 6,251 $ 28,842 35,093.00 9,723 1999 2005 40 1 West Elm Street W. Conshohocken PA - 3,557 14,249 3,372 3,557 $ 17,621 21,178.00 5,673 1999 2005 40 Four Tower Bridge (200 Barr Harbor Drive) W. Conshohocken PA 9,526 6,000 14,734 19 6,000 $ 14,753 20,753.00 369 1998 2018 40 Initial Cost Gross Amount Which Carried December 31, 2018 Property Name City State Encumbrances (a) Land Building & Improvements Net Improvements (Retirements) Since Acquisition Land Building & Improvements Total (b) Accumulated Depreciation at December 31, 2018 (c) Year of Construction Year Acquired Depreciable Life PHILADELPHIA CBD Cira Centre (2929 Arch Street) Philadelphia PA - - 208,570 (13,907 ) 12,586 $ 182,077 194,663.00 65,851 2005 N/A 40 Three Logan Square (1717 Arch Street) Philadelphia PA - - 98,188 63,532 25,195 $ 136,525 161,720.00 34,908 1990 2010 40 Two Commerce Square (2001 Market Street) Philadelphia PA 110,518 15,323 120,200 24,144 15,323 $ 144,344 159,667.00 22,184 1992 2013 40 One Logan Square (130 North 18th Street) Philadelphia PA - 14,496 107,736 28,657 14,473 $ 136,416 150,889.00 56,850 1998 2004 34 Two Logan Square (100 North 18th Street) Philadelphia PA 82,805 16,066 100,255 19,053 16,066 $ 119,308 135,374.00 45,211 1988 2004 36 One Commerce Square (2005 Market Street) Philadelphia PA 120,183 15,161 105,021 27,997 15,160 $ 133,019 148,179.00 19,848 1987 2013 40 Cira Centre South Garage (129 South 30th Street) Philadelphia PA - - 76,008 14,183 - $ 90,191 90,191.00 17,015 2010 N/A 40 1900 Market Street Philadelphia PA - 7,768 17,263 51,364 7,768 $ 68,627 76,395.00 11,327 1981 2012 30 3020 Market Street Philadelphia PA - - 21,417 8,100 - $ 29,517 29,517.00 9,013 1959 2011 26 The Lift at Juniper Street (101 - 103 Juniper Street) Philadelphia PA - - 14,401 (14,401 ) - $ - - - 2010 2006 40 618-634 Market Street (d) Philadelphia PA - 13,365 5,791 1,952 13,365 $ 7,743 21,108.00 4,601 1966 2015 5 FMC Tower at Cira Centre South (2929 Walnut Street) Philadelphia PA - - 400,294 12,964 - $ 413,258 413,258.00 31,439 2016 N/A 40 2100 Market Street (e) Philadelphia PA - 18,827 - 6,594 18,854 $ 6,567 25,421.00 547 N/A 2015 N/A 3000 Market Street (f) Philadelphia PA - 18,924 13,080 600 18,924 $ 13,680 32,604.00 1,720 1937 2017 12 The Bulletin Building (3025 Market Street) (f) Philadelphia PA - - 24,377 6,968 - $ 31,345 31,345.00 978 1953 2017 40 3001-3003 JFK Boulevard (h) Philadelphia PA - - - 78 - $ 78 78.00 2 N/A 2018 N/A 3025 JFK Boulevard (h) Philadelphia PA - - - - - $ - - - N/A 2018 N/A METROPOLITAN WASHINGTON, D.C. 6600 Rockledge Drive Bethesda MD - - 37,421 9,349 - $ 46,770 46,770.00 13,469 1981 2006 50 2340 Dulles Corner Boulevard Herndon VA - - - 82,248 16,129 $ 66,119 82,248.00 20,429 1987 2006 40 1676 International Drive Mclean VA - 18,437 97,538 3,412 18,785 $ 100,602 119,387.00 25,864 1999 2006 55 8260 Greensboro Drive Mclean VA - 7,952 33,964 4,559 8,102 $ 38,373 46,475.00 10,083 1980 2006 52 2273 Research Boulevard Rockville MD - 5,167 31,110 4,538 5,237 $ 35,578 40,815.00 10,624 1999 2006 45 2275 Research Boulevard Rockville MD - 5,059 29,668 8,034 5,154 $ 37,607 42,761.00 12,388 1990 2006 45 2277 Research Boulevard Rockville MD - 4,649 26,952 18,854 4,733 $ 45,722 50,455.00 14,723 1986 2006 45 1900 Gallows Road Vienna VA - 7,797 47,817 (2,381 ) 5,566 $ 47,667 53,233.00 19,418 1989 2006 52 8521 Leesburg Pike Vienna VA - 4,316 30,885 6,826 4,397 $ 37,630 42,027.00 11,046 1984 2006 51 AUSTIN, TX 11501 Burnet Road - Building 1 Austin TX - 3,755 22,702 117 3,755 $ 22,819 26,574.00 2,489 1991 2015 35 11501 Burnet Road - Building 2 Austin TX - 2,732 16,305 1,562 2,732 $ 17,867 20,599.00 2,268 1991 2015 35 11501 Burnet Road - Building 3 Austin TX - 3,688 22,348 115 3,688 $ 22,463 26,151.00 2,449 1991 2015 35 11501 Burnet Road - Building 4 Austin TX - 2,614 15,740 81 2,614 $ 15,821 18,435.00 1,725 1991 2015 35 11501 Burnet Road - Building 5 Austin TX - 3,689 22,354 115 3,689 $ 22,469 26,158.00 2,450 1991 2015 35 11501 Burnet Road - Building 6 (g) Austin TX - 2,676 15,972 13,396 2,676 $ 29,368 32,044.00 1,387 1991 2015 40 11501 Burnet Road - Building 8 Austin TX - 1,400 7,422 100 1,400 $ 7,522 8,922.00 828 1991 2015 35 11501 Burnet Road - Parking Garage Austin TX - - 19,826 102 - $ 19,928 19,928.00 2,884 1991 2015 35 One Barton Skyway (1501 South MoPac Expressway) Austin TX - 10,496 47,670 (39 ) 10,495 $ 47,632 58,127.00 103 1999 2018 40 Two Barton Skyway (1601 South MoPac Expressway) Austin TX - 10,849 53,868 (40 ) 10,848 $ 53,829 64,677.00 116 2000 2018 40 Three Barton Skyway (1221 South MoPac Expressway) Austin TX - 10,374 47,624 (39 ) 10,373 $ 47,586 57,959.00 100 2001 2018 40 Four Barton Skyway (1301 South MoPac Expressway) Austin TX - 13,301 57,041 (40 ) 13,300 $ 57,002 70,302.00 121 2001 2018 40 Initial Cost Gross Amount Which Carried December 31, 2018 Property Name City State Encumbrances (a) Land Building & Improvements Net Improvements (Retirements) Since Acquisition Land Building & Improvements Total (b) Accumulated Depreciation at December 31, 2018 (c) Year of Construction Year Acquired Depreciable Life Four Points Centre (11305 Four Points Drive) Austin TX - 7,800 43,581 (40 ) 7,800 $ 43,541 51,341.00 91 2008 2018 40 River Place - Building 1 (6500 River Place Boulevard) Austin TX - 2,004 17,680 (39 ) 2,004 $ 17,641 19,645.00 36 2000 2018 40 River Place - Building 2 (6500 River Place Boulevard) Austin TX - 3,137 29,254 (40 ) 3,137 $ 29,214 32,351.00 61 2000 2018 40 River Place - Building 3 (6500 River Place Boulevard) Austin TX - 3,064 26,705 (40 ) 3,064 $ 26,665 29,729.00 56 2000 2018 40 River Place - Building 4 (6500 River Place Boulevard Austin TX - 2,273 18,617 (39 ) 2,273 $ 18,578 20,851.00 39 2000 2018 40 River Place - Building 5 (6500 River Place Boulevard) Austin TX - 1,752 14,315 (39 ) 1,752 $ 14,276 16,028.00 30 2001 2018 40 River Place - Building 6 (6500 River Place Boulevard) Austin TX - 1,598 12,945 (39 ) 1,598 $ 12,906 14,504.00 27 2001 2018 40 River Place - Building 7 (6500 River Place Boulevard) Austin TX - 1,801 16,486 (39 ) 1,801 $ 16,447 18,248.00 35 2002 2018 40 Quarry Lake II (4516 Seton Center Parkway) Austin TX - 3,970 30,546 604 3,867 $ 31,253 35,120.00 - 1998 2018 40 OTHER 10 Foster Avenue Gibbsboro NJ - 244 971 69 244 $ 1,040 1,284.00 597 1983 1997 40 7 Foster Avenue Gibbsboro NJ - 231 921 31 231 $ 952 1,183.00 522 1983 1997 40 2 Foster Avenue Gibbsboro NJ - 185 730 11 185 $ 741 926.00 741 1974 1997 40 4 Foster Avenue Gibbsboro NJ - 183 726 6 183 $ 732 915.00 732 1974 1997 40 1 Foster Avenue Gibbsboro NJ - 93 364 8 93 $ 372 465.00 372 1972 1997 40 5 U.S. Avenue Gibbsboro NJ - 21 81 2 21 $ 83 104.00 59 1987 1997 40 5 Foster Avenue Gibbsboro NJ - 9 32 3 9 $ 35 44.00 25 1968 1997 40 Main Street - Plaza 1000 Voorhees NJ - 2,732 10,942 376 2,732 $ 11,318 14,050.00 11,064 1988 1997 40 Main Street - Piazza Voorhees NJ - 696 2,802 3,701 705 $ 6,494 7,199.00 3,124 1990 1997 40 Main Street - Promenade Voorhees NJ - 532 2,052 405 532 $ 2,457 2,989.00 1,445 1988 1997 40 920 North King Street Wilmington DE - 6,141 21,140 7,969 6,141 $ 29,109 35,250.00 11,593 1989 2004 30 300 Delaware Avenue Wilmington DE - 6,369 13,739 1,991 6,369 $ 15,729 22,099.00 8,202 1989 2004 23 Total: $ 323,032 $ 453,723 $ 2,863,832 $ 635,764 $ 508,363 $ 3,444,955 $ 3,953,319 $ 865,462 (a) Excludes the effect of any net interest premium/(discount) and deferred financing costs. (b) Reconciliation of Real Estate: The following table reconciles the real estate investments from January 1, 2016 to December 31, 2018 (in thousands): 2018 2017 2016 Balance at beginning of year $ 3,832,348 $ 3,659,886 $ 4,487,588 Additions: Acquisitions 509,654 62,586 - Capital expenditures and assets placed into service 129,274 356,857 213,996 Less: Dispositions/impairments/placed into redevelopment (469,441 ) (189,395 ) (962,676 ) Retirements (48,516 ) (57,586 ) (79,022 ) Balance at end of year $ 3,953,319 $ 3,832,348 $ 3,659,886 Less: Assets held for sale - - (73,591 ) Per consolidated balance sheet $ 3,953,319 $ 3,832,348 $ 3,586,295 The aggregate cost for federal income tax purposes is $3.3 billion as of December 31, 2018. (c) Reconciliation of Accumulated Depreciation: The following table reconciles the accumulated depreciation on real estate investments from January 1, 2016 to December 31, 2018 (in thousands): 2018 2017 2016 Balance at beginning of year $ 895,091 $ 885,392 $ 1,080,616 Additions: Depreciation expense 135,473 135,822 131,859 Less: Dispositions/impairments/placed into redevelopment (117,589 ) (74,178 ) (250,110 ) Retirements (47,513 ) (51,945 ) (76,973 ) Balance at end of year $ 865,462 $ 895,091 $ 885,392 Less: Assets held for sale - - (32,916 ) Per consolidated balance sheet $ 865,462 $ 895,091 $ 852,476 (d) At acquisition it was determined that the useful life of the parking structure is five years, which reflects the expected demolition date. (e) Building and improvements consists of capital improvements, which are depreciated over the lease term. (f) Reflects original construction date. Significant improvements were made to 3000 Market Street in 1988 and The Bulletin Building in 2012. (g) The property was partially placed into service during 2017. (h) Represent leasehold interests in two land parcels, each acquired through prepaid 99-year

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Out of Period Adjustment	Out of Period Adjustment The Company recorded $1.2 million of impairment charges during the quarter ended December 31, 2016, which should have been recorded in the consolidated financial statements for the three-month period ended March 31, 2017 and the year ended December 31, 2017. Management concluded that this misstatement was not material to any prior period, nor was it material to the consolidated financial statements as of and for the twelve-month periods ended December 31, 2017 and 2016.
Reclassifications and Adoption of New Accounting Guidance	Reclassifications and Adoption of New Accounting Guidance Through the year ended December 31, 2017, the Company included $0.6 million of income tax benefit in general and administrative expenses. During the fourth quarter of 2017, the Company began disaggregating the income tax provision/benefit in the consolidated statements of operations. As a result, in the statements of operations for the year ended December 31, 2017 the Company reclassified $0.6 million of net income tax benefit out of general and administrative expenses into the “Income tax (provision) benefit” caption in the consolidated statements of operations to provide comparative presentation. During the first quarter of 2018, the Company adopted Financial Accounting Standards Board (the “FASB”) Accounting Standards Update (“ASU”) No. 2016-18, which requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents and amounts described as restricted cash or cash equivalents. Beginning-of-period and end-of-period total amounts shown on the statement of cash flows should include restricted 0.4 1.3 1.3 . I n accordance with ASC 360, and in response to the SEC’s “Disclosure Update and Simplification” release effective November 5, 2018, the Company reclassified gains and losses resulting from wholly owned real estate dispositions from the “Other income (expense)” section to the “Operating income” section within its consolidated statements of operations. As a result, in the consolidated statements of operations for the years ended December 31, 2018, 2017 and 2016, the Company reclassified the following amounts to the “Operating income” section: Caption 2018 2017 2016 Net gain on disposition of real estate $ 2,932 $ 31,657 $ 116,983 Net gain on sale of undepreciated real estate 3,040 953 9,232 Total gain on sale of real estate $ 5,972 $ 32,610 $ 126,215
Principles of Consolidation	Principles of Consolidation The Company consolidates variable interest entities (“VIEs”) in which it is considered to be the primary beneficiary. VIEs are entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or that the holders of the equity investment at risk do not have a controlling financial interest. The primary beneficiary is defined by the entity having both of the following characteristics: (i) the power to direct those matters that most significantly impact the activities of the VIE and (ii) the obligation to absorb losses or the right to receive benefits of the VIE that could potentially be significant to the VIE. For entities that the Company has the obligations to fund losses, its maximum exposure to loss is not limited to the carrying amount of its investments. When an entity is not deemed to be a VIE, the Company consolidates entities for which it has significant decision making control over the entity’s operations. The Company’s judgement with respect to its level of influence or control of an entity involves consideration of various factors including the form of the Company’s ownership interest, its representation in the entity’s governance, the size of its investment (including loans), estimates of future cash flows, its ability to participate in policy making decisions and the rights of the other investors to participate in the decision making process and to replace the Company as manager and/or liquidate the venture, if applicable. The Company’s assessment of its influence or control over an entity affects the presentation of these investments in the Company’s consolidated financial statements. In addition to evaluating control rights, the Company consolidates entities in which the outside partner has no substantive kick-out rights to remove the Company as managing member. The portion of the consolidated entities that are not owned by the Company is presented as noncontrolling interest as of and during the periods consolidated. All intercompany transactions have been eliminated in consolidation. The Company continuously assesses its determination of the primary beneficiary for each entity and assesses reconsideration events that may cause a change in the original determinations . As of December 31, 2018 and 2017, the Company included in its consolidated balance sheets consolidated VIEs having total assets of $414.3 million and $412.9 million, respectively, and total liabilities of $254.1 million and $250.4 million, respectively.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates. Management makes significant estimates regarding revenue, valuation of real estate and related intangible assets and liabilities, impairment of long-lived assets, impairment of investments in Real Estate Ventures allowance for doubtful accounts, variable employee compensation, deferred costs and contingencies.
Operating Properties	Operating Properties Operating properties are carried at historical cost less accumulated depreciation and impairment losses. The value of operating properties reflects their purchase price or development cost. Acquisition costs related to business combinations are expensed as incurred, whereas the costs related to asset acquisitions are capitalized as incurred. Costs incurred for the renovation and betterment of an operating property are capitalized to the Company’s investment in that property. Ordinary repairs and maintenance are expensed as incurred.
Purchase Price Allocation	Purchase Price Allocation For acquisitions of real estate or in-substance real estate that are accounted for as business combinations, we recognize the assets acquired (including the intangible value of acquired above- or below-market leases, acquired in-place leases and tenant relationship values), liabilities assumed, noncontrolling interests, and previously existing ownership interests at fair value as of the acquisition date. Any excess (deficit) of the consideration transferred relative to the fair value of the net assets acquired is accounted for as goodwill (bargain purchase gain). Acquisition costs related to business combinations are expensed as incurred. Acquisitions of real estate and in-substance real estate that do not meet the definition of a business are accounted for as asset acquisitions. The accounting model for asset acquisitions is similar to the accounting model for business combinations except that the acquisition consideration (including acquisition costs) is allocated to the individual assets acquired and liabilities assumed on a relative fair value basis. As a result, asset acquisitions do not result in recognition of goodwill or a bargain purchase gain. Additionally, because the accounting model for asset acquisitions is a cost accumulation model, preexisting interests in the acquired assets, if any, are not remeasured to fair value but continue to be accounted for at their historical cost. Direct acquisition costs are capitalized if an asset acquisition is probable. If we determine that an asset acquisition is no longer probable, no new costs are capitalized and all capitalized costs that are not recoverable are written off. The Company adopted ASU 2017-01 – Business Combinations as of January 1, 2017, which amended the definition of a business. The purchase price is allocated to the acquired assets and assumed liabilities, including land and buildings, as if vacant based on highest and best use for the acquired assets. The Company assesses and considers fair value of the operating properties based on estimated cash flow projections that utilize discount and/or capitalization rates that it deems appropriate, as well as available market information. Estimates of future cash flows are based on a number of factors including the historical operating results, known and anticipated trends, and market and economic conditions. The Company allocates the purchase price of properties considered to be business combinations and asset acquisitions to net tangible and identified intangible assets acquired based on fair values. Above-market and below-market in-place lease values for acquired properties are recorded based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to the in-place leases and (ii) the Company’s estimate of the fair market lease rates for the corresponding in-place leases, measured over a period equal to the remaining non-cancelable term of the lease (including the below market fixed renewal period, if applicable). Capitalized above-market lease values are amortized as a reduction of rental income over the remaining non-cancelable terms of the respective leases. Capitalized below-market lease values are amortized as an increase to rental income over the remaining non-cancelable terms of the respective leases, including any below market fixed-rate renewal option periods that are considered probable. Other intangible assets also include in-place leases based on the Company’s evaluation of the specific characteristics of each tenant’s lease and the Company’s overall relationship with the respective tenant. The Company estimates the cost to execute leases with terms similar to the remaining lease terms of the in-place leases, including leasing commissions, legal and other related expenses. This intangible asset is amortized to expense over the remaining term of the respective leases and any fixed-rate bargain renewal periods. Company estimates of value are made using methods similar to those used by independent appraisers or by using independent appraisals. Factors considered by the Company in this analysis include an estimate of the carrying costs during the expected lease-up periods considering current market conditions and costs to execute similar leases. In estimating carrying costs, the Company includes real estate taxes, insurance and other operating expenses and estimates of lost rents at market rates during the expected lease-up periods, which primarily range from four to twelve months. The Company also considers information obtained about each property as a result of its pre-acquisition due diligence, marketing and leasing activities in estimating the fair value of the tangible and intangible assets acquired. The Company also uses the information obtained as a result of its pre-acquisition due diligence as part of its consideration of the accounting standard governing asset retirement obligations and when necessary, will record a conditional asset retirement obligation as part of its purchase price. The Company also evaluates tenant relationships on a tenant-specific basis. On most of the Company’s acquisitions, this intangible has been deemed immaterial, in which case no related intangible asset value is assigned. In the event that a tenant terminates its lease, the unamortized portion of each intangible, including in-place lease values and tenant relationship values, is charged to expense and market rate adjustments (above or below) is recorded to revenue. The Company records development acquisitions that do not meet the accounting criteria to be accounted for as business combinations at the purchase price paid. Costs directly associated with development acquisitions accounted for as asset acquisitions are capitalized as part of the cost of the acquisition.
Depreciation and Amortization	Depreciation and Amortization The costs of buildings and improvements are depreciated using the straight-line method based on the following useful lives: buildings and improvements (5 to 55 years) and tenant improvements (the shorter of (i) the life of the asset, 1 to 16 years, or (ii) the lease term).
Construction-in-Progress	Construction-in-Progress Project costs directly associated with the development and construction of a real estate project are capitalized as construction-in-progress. Construction-in-progress also includes costs related to ongoing tenant improvement projects. In addition, interest, real estate taxes and other expenses that are directly associated with the Company’s development activities are capitalized until the property is placed in service. Interest expense is capitalized using the Company’s weighted average interest rate. Internal direct costs are capitalized to projects in which qualifying expenditures are being incurred. Internal direct construction costs totaling $7.0 million in 2018, $6.1 million in 2017, $6.7 million in 2016 and interest totaling $3.6 million in 2018, $3.1 million in 2017, and $10.9 million in 2016 were capitalized related to the development of certain properties and land holdings. During the years ended December 31, 2018, 2017 and 2016, the Company’s internal direct construction costs are comprised entirely of capitalized salaries. The following table shows the amount of compensation costs (including bonuses and benefits) capitalized for the years presented (in thousands): December 31, 2018 2017 2016 Development $ 3,185 $ 4,390 $ 3,182 Redevelopment 968 319 144 Tenant Improvements 2,811 1,354 3,391 Total $ 6,964 $ 6,063 $ 6,717
Impairment or Disposal of Long-Lived Assets	Impairment or Disposal of Long-Lived Assets The Company reviews its long-lived assets for impairment following the end of each quarter using cash flow projections and estimated fair values for each of its properties where events or changes in circumstances indicate that the carrying amounts may not be recoverable. The Company updates leasing and other assumptions regularly, paying particular attention to properties where there is an event or change in circumstances that indicates an impairment in value. Additionally, the Company considers strategic decisions regarding the future development plans for property under development and other market factors. For long-lived assets to be held and used, the Company analyzes recoverability based on the estimated undiscounted future cash flows expected to be generated from the operations and eventual disposition of the assets over, in most cases, a 10-year hold period. If there is significant possibility that the Company will dispose of assets earlier, it analyzes the recoverability using a probability weighted analysis of the undiscounted future cash flows expected to be generated from the operations and eventual disposition of each asset using various probable hold periods. If the recovery analysis indicates that the carrying value of the tested property is not recoverable, the property is written down to its fair value and an impairment loss is recognized. In such case, an impairment loss is recognized in the amount of the excess of the carrying amount of the asset over its fair value. If and when the Company’s plans change, it revises its recoverability analysis to use cash flows expected from operations and eventual disposition of each asset using hold periods that are consistent with its revised plans. Estimated cash flows used in such analysis are based on the Company’s plans for the property and its views of market economic conditions. The estimates consider factors such as current and future rental rates, occupancies for the tested property and comparable properties, estimated operating and capital expenditures and recent sales data for comparable properties; most of these factors are derived from market data obtained from real estate leasing and brokerage firms and the Company’s direct experience with the properties and their markets.
Assets Held for Sale	Assets Held for Sale The Company generally considers assets to be “held for sale” when the transaction has been approved by its Board of Trustees, or by officers vested with authority to approve the transaction, and there are no known significant contingencies relating to the sale of the property within one year of the consideration date and the consummation of the transaction is otherwise considered probable. When a property is designated as held for sale, the Company stops depreciating the property and estimates the property’s fair value, net of selling costs. If the determination is made that the estimated fair value, net of selling costs, is less than the net carrying value of the property, an impairment loss is recognized, reducing the net carrying value of the property to estimated fair value less selling costs. For periods in which a property is classified as held for sale, the Company classifies the assets and liabilities, as applicable, of the property as “held for sale” on the consolidated balance sheet for such periods. The relevant accounting guidance for impairments requires that qualifying assets and liabilities and the results of operations that have been sold, or otherwise qualify as “held for sale,” be presented as discontinued operations in all periods presented if the disposal represents a strategic shift that has, or will have, a major effect on the Company’s operations and financial results. The components of the property’s net income that is reflected as discontinued operations include the net gain (or loss) upon the disposition of the property held for sale, operating results, depreciation and interest expense (if the property is subject to a secured loan).
Impairment of Land Held for Development	Impairment of Land Held for Development When demand for build-to-suit office space declines and the ability to sell land held for development deteriorates, or other market factors indicate possible impairment in the recoverability of land held for development, it is reviewed for impairment by comparing its fair value to its carrying value. If the estimated sales value is less than the carrying value, the carrying value is written down to its estimated fair value.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents are highly-liquid investments with original maturities of three months or less. The Company maintains cash equivalents in money market accounts with financial institutions in excess of insured limits, but believes this risk is mitigated by only investing in or through major financial institutions. The Company does not invest its available cash balances in money market funds, as such available cash balances are appropriately reflected as cash and cash equivalents on the consolidated balance sheets.
Restricted Cash	Restricted Cash Restricted cash consists of cash held as collateral to provide credit enhancement for the Company’s mortgage debt, cash for property taxes, capital expenditures and tenant improvements. Escrows also include cash held by qualified intermediaries for possible investments in like-kind exchanges in accordance with Section 1031 of the Internal Revenue Code in connection with sales of the Company’s properties. Restricted cash is included in the “Other assets” caption in the consolidated balance sheets.
Accounts Receivable And Accrued Rent Receivable	Accounts Receivable and Accrued Rent Receivable Generally, leases with tenants are accounted for as operating leases. Minimum lease payments under tenant leases are recognized on a straight-line basis over the term of the related lease. The cumulative difference between lease revenue recognized under the straight-line method and contractual lease payment terms are recorded as “Accrued rent receivable, net” on the consolidated balance sheets. Included in current tenant receivables are tenant reimbursements which are comprised of amounts recoverable from tenants for common area maintenance expenses and certain other recoverable expenses that are recognized as revenue in the period in which the related expenses are incurred. As of December 31, 2018 and 2017, no tenant represented more than 10% of accounts receivable and accrued rent receivable. Tenant receivables and accrued rent receivables are carried net of the allowances for doubtful accounts of $1.7 million and $11.3 million in 2018, respectively, and $3.5 million and $13.6 million in 2017, respectively. The tenant receivables allowance is an estimate based on two calculations that are combined to determine the total amount reserved. First, the Company evaluates specific accounts where it has determined that a tenant may have an inability to meet its financial obligations. In these situations, the Company uses its judgment, based on the facts and circumstances, and records a specific reserve for that tenant against amounts due to reduce the receivable to the amount that the Company expects to collect. These reserves are reevaluated and adjusted as additional information becomes available. Second, a reserve is established for all tenants based on a range of percentages applied to receivable aging categories for tenant receivables. For accrued rent receivables, the Company considers the results of the evaluation of specific accounts and also considers other factors including assigning risk factors to different industries based on its tenants Standard Industrial Classification (SIC). The accrued rent receivable allowance percentages are also based on historical collection and write-off experience adjusted for current market conditions, which requires management’s judgments.
Investments in Unconsolidated Real Estate Ventures	Investments in Unconsolidated Real Estate Ventures Under the equity method, investments in unconsolidated Real Estate Ventures are recorded initially at cost and subsequently adjusted for equity in earnings, contributions, distributions and impairments. For Real Estate Ventures that are constructing assets to commence planned principal operations, the Company capitalizes interest expense to the extent that it is recoverable using the Company’s weighted average interest rate of consolidated debt and its investment balance as a basis. Planned principal operations commence when a property is available to lease and at that point in time, the Company ceases capitalizing interest to its investment basis. During the twelve months ended December 31, 2018, the Company did not capitalize any interest expense. During the twelve months ended December 31, 2017 and 2016, the Company capitalized interest expense of $0.4 million and $1.9 million. On a periodic basis, management also assesses whether there are any indicators that the value of the Company’s investments in unconsolidated Real Estate Ventures may be other than temporarily impaired. An investment is impaired only if the value of the investment, as estimated by management, is less than the carrying value of the investment and the decline is other than temporary. To the extent that an impairment has occurred, the loss shall be measured as the excess of the carrying amount of the investment over the fair value of the investment, as estimated by management. Management is required to make significant judgements about the fair value of its ownership interests to determine if an impairment exists. Fair value is determined through various valuation techniques, including but not limited to, discounted cash flow models, quoted market values and third party appraisals. When the Company acquires an interest in or contributes assets to a real estate venture project, the difference between the Company’s cost basis in the investment and the value of the real estate venture or asset contributed is amortized over the life of the related assets, intangibles and liabilities and such adjustment is included in the Company’s share of equity in income of unconsolidated Real Estate Ventures. For purposes of cash flow presentation, distributions from unconsolidated Real Estate Ventures are presented as part of operating activities when they are considered as a return on investments. The Company elected, in connection with its adoption of ASU 2016-15, “Classification of Certain Cash Receipts and Cash Payments” (ASU 2016-15) during the fourth quarter of 2016, to continue to account for
Deferred Costs	Deferred Costs Costs incurred in connection with property leasing are capitalized as deferred leasing costs. Deferred leasing costs consist primarily of leasing commissions and internal leasing costs that are amortized using the straight-line method over the life of the respective lease which generally ranges from 1 to 16 years. Management re-evaluates the remaining useful lives of leasing costs as economic and market conditions change.
Notes Receivable	Notes Receivable The Company accounts for notes receivable on its balance sheet at amortized cost, net of allowance for loan losses. Interest income is recognized over the term of the notes receivable and is calculated based on the terms of the contractual terms of each note agreement. Notes receivable are placed on nonaccrual status when management determines, after considering economic and business conditions and collection efforts, that the loans are impaired or collection of interest is doubtful. Uncollectible interest previously accrued is recognized as bad debt expense. Interest income on nonaccrual loans is recognized only to the extent that cash payments are received. On June 26, 2018, the Company provided a $44.4 million mortgage loan with a 4.0% stated interest rate and maturing on June 25, 2023, to Brandywine 1919 Ventures, an unconsolidated real estate venture in which the Company holds a 50% ownership interest, and recorded a note receivable of $44.4 million. Additionally, a note receivable was given to an unaffiliated third party during the third quarter of 2016 to facilitate its acquisition and development of an industrial facility located in Pennsauken, New Jersey. The Company evaluated its investments in the notes receivable under ASC 310, “Receivables” and determined that the loans were provided at market terms and the Company does not participate in the residual profits of the unaffiliated third parties. Accordingly, the investments, totaling $47.8 million as of December 31, 2018 and $3.5 million as of December 31, 2017, have been classified on the Company’s consolidated balance sheets as notes receivable within the “Other assets” caption on the accompanying consolidated balance sheets.
Deferred Financing Costs	Deferred Financing Costs Costs incurred in connection with debt financing are capitalized as a direct deduction from the carrying value of the debt, except for costs capitalized related to the Company’s revolving credit facility, which are capitalized within the “Deferred costs, net” caption on the accompanying consolidated balance sheets. Deferred financing costs are charged to interest expense over the terms of the related debt agreements. Deferred financing costs consist primarily of loan fees which are amortized over the related loan term on a basis that approximates the effective interest method. Deferred financing costs are accelerated, when debt is extinguished, as part of the “Interest expense-amortization of deferred financing costs” caption within the Company’s consolidated statements of operations. Original issue discounts are recognized as part of the gain or loss on extinguishment of debt, as appropriate.
Revenue Recognition	Revenue Recognition In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606). Under Topic 606, revenue is recognized when a customer obtains control of promised goods or services and is recognized at an amount that reflects the consideration expected to be received in exchange for such goods or services. In addition, Topic 606 requires disclosure of the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. The Company adopted Topic 606 in the first quarter of 2018 using the modified retrospective method. This adoption, which required the Company to evaluate incomplete contracts as of January 1, 2018, related to the Company’s point of sale revenue, management, leasing and development fee arrangements and other sundry income. The Company’s analysis of incomplete contracts resulted in no cumulative effect adjustment to the consolidated balance sheets and statements of operations presented in its consolidated financial statements. Results for reporting periods beginning after January 1, 2018 are presented under Topic 606. The new guidance provides a unified model to determine how revenue is recognized. To determine the proper amount of revenue to be recognized, the Company performs the following steps: (i) identify the contract with the customer, (ii) identify the performance obligations within the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations and (v) recognize revenue when (or as) a performance obligation is satisfied. The following is a summary of revenue earned by the Company’s reportable segments (see Note 17, “Segment Information,” Twelve-month period ended December 31, 2018 Philadelphia CBD Pennsylvania Suburbs Metropolitan Washington, D.C. Austin, Texas Other Corporate Total Base rent $ 164,369 $ 118,628 $ 80,858 $ 21,757 $ 8,400 $ (1,964 ) $ 392,048 Straight-line rent 11,867 2,851 (1,577 ) 116 201 (449 ) 13,009 Point of sale 23,528 258 1,062 521 230 - 25,599 Total rents 199,764 121,737 80,343 22,394 8,831 (2,413 ) 430,656 Tenant reimbursements 51,572 14,440 3,519 10,736 2,832 (474 ) 82,625 Termination fees 192 1,435 136 - - - 1,763 Third party management fees, labor reimbursement and leasing 855 25 5,793 5,455 4,951 5,478 22,557 Other income 4,334 642 517 80 143 1,028 6,744 Total revenue $ 256,717 $ 138,279 $ 90,308 $ 38,665 $ 16,757 $ 3,619 $ 544,345 (a) Corporate includes intercompany eliminations necessary to reconcile to consolidated Company totals. Rental Revenue The Company owns, operates and manages commercial real estate. The Company’s primary source of revenue is leases which fall under the scope of Leases (Topic 840). Rental revenue is recognized on a straight-line basis over the term of the leases from the later of the date of the commencement of the lease or the date of acquisition of the property subject to existing leases. The straight-line rent adjustment increased revenue by approximately $10.4 million in 2018, $24.9 million in 2017 and $26.3 million in 2016. Deferred rents on the balance sheet represent rental revenue received prior to their due dates and amounts paid by the tenant for certain improvements considered to be landlord assets that will remain as the Company’s property at the end of the tenant’s lease term. The amortization of the amounts paid by the tenant for such improvements is calculated on a straight-line basis over the term of the tenant’s lease and is a component of straight-line rental income and increased revenue by $1.8 million in 2018, $2.2 million in 2017 and $2.1 million in 2016. Lease incentives, which are included as reductions of rental revenue in the accompanying consolidated statements of operations, are recognized on a straight-line basis over the term of the lease. Lease incentives decreased revenue by $1.5 million in 2018, $1.8 million in 2017 and $2.0 million in 2016. In addition, the Company’s rental revenue is impacted by the Company’s determination of whether improvements to the properties, whether made by the Company or by the tenant, are landlord assets. The determination of whether an improvement is a landlord asset requires judgment. In making this judgment, the Company’s primary consideration is whether the improvement would be utilizable by another tenant upon move out of the improved space by the then-existing tenant. If the Company has funded an improvement that it determines not to be landlord assets, then it treats the cost of the improvement as a lease incentive. If the tenant has funded the improvement that the Company determines to be landlord assets, then the Company treats the costs of the improvement as deferred revenue and amortizes this cost into revenue over the lease term. For certain leases, the Company makes significant assumptions and judgments in determining the lease term, including assumptions when the lease provides the tenant with an early termination option. The lease term impacts the period over which the Company determines and records minimum rents and also impacts the period over which the Company amortizes lease-related costs. No tenant represented greater than 10% of the Company’s rental revenue in 2018, 2017 or 2016. Point of Sale Revenue Point of sale revenue consists of parking, restaurant and flexible stay revenue from the Company’s hotel operations. Point of sale service obligations are performed daily, and the customer obtains control of those services simultaneously as they are performed. Accordingly, revenue is recorded on an accrual basis as it is earned, coinciding with the services that are provided to the Company’s customers. Tenant Reimbursements The Company’s leases also typically provide for tenant reimbursement of a portion of common area maintenance expenses and other operating expenses to the extent that a tenant’s pro rata share of expenses exceeds a base year level set in the lease or to the extent that the tenant has a lease on a triple net basis. The Company also contracts with third-party vendors and suppliers for goods and services to fulfill certain of the Company’s obligations to tenants. The Company is reimbursed by tenants for these goods and services in the period that the expenses are incurred based on the terms of the lease agreements with each tenant. Recoveries from tenants, consisting of amounts due from tenants for common area maintenance expenses, real estate taxes and other recoverable costs are recognized as revenue in the period during which the expenses are incurred. Tenant reimbursements are recognized and presented in accordance with accounting guidance which requires that these reimbursements be recorded on a gross basis because the Company is generally the primary obligor with respect to the goods and services the purchase of which gives rise to the reimbursement obligation; because the Company has discretion in selecting the vendors and suppliers; and because the Company bears the credit risk in the event they do not reimburse the Company. The Company also receives payments from third parties for reimbursement of a portion of the payroll and payroll-related costs for certain of the Company’s personnel allocated to perform services for third parties and reflects these payments on a gross basis. Termination Fees The Company recognizes fees received for lease terminations as revenue and writes off against such revenue any deferred rents receivable. The resulting net amount is the net revenue from the early termination of the leases. When a tenant's lease for space in a property is terminated early but the tenant continues to lease such space under a new or modified lease in the property, the net revenue from the early termination of the lease is recognized evenly over the remaining life of the new or modified lease in place on that property, unless the Company cannot determine that collectability of the lease termination revenue is reasonably assured. Third party management fees, labor reimbursement and leasing The Company performs property management services for third-party property owners of real estate that consist of: (i) providing leasing services, (ii) property inspections, (iii) repairs and maintenance monitoring, and (iv) financial and accounting oversight. For these services, the Company earns management fees monthly, which are based on a fixed percentage of each managed property’s financial results, and is reimbursed for the labor costs incurred by its property management employees as services are rendered to the property owners. The Company determined that control over the services is passed to its customers simultaneously as performance occurs. Accordingly, management fee revenue is earned as the services are provided to the Company’s customers. Lease commissions are earned when the Company, as a broker for the third party property owner, executes a lease agreement with a tenant. Based on the terms of the Company’s lease commission contracts, it determined that control is transferred to the customer upon execution of each lease agreement. The Company’s lease commissions are earned based on a fixed percentage of rental income generated for each executed lease agreement and there is no variable income component. Development fee revenue is earned through two different sources: (i) the Company performs development services for third parties as an agent and earns fixed development fees based on a percentage of construction costs incurred over the construction period, and (ii) the Company acts as a general contractor on behalf of one of its managed real estate ventures. The Company acts as the principal construction company for the real estate ventures and records gross revenue as it provides construction services based on the quantifiable construction outputs. In applying the cost based output method of revenue recognition, the Company uses the actual costs incurred relative to the total estimated costs to determine its progress towards contract completion and to calculate the corresponding gross revenue and gross profit to recognize. For any costs that do not contribute to satisfying the Company’s performance obligations, it excludes such costs from its output methods of revenue recognition as the amounts are not reflective of transferring control of the outputs to the customer. The use of estimates in this calculation involves significant judgment. The Company receives leasing commission income, property management fees and third party development fees. Leasing commission income is earned based on a percentage of gross rental income upon a tenant signing a lease with a third party lessor. Property management fees are recorded and earned based on a percentage of collected rents at the properties under management, and not on a straight-line basis because such fees are contingent upon the collection of rents. The Company records development fees on a percentage of completion basis. As of December 31, 2018, the Company has $1.5 million of accounts receivable associated with the Company’s third party management contracts. Other Income Other income primarily consists of sundry revenue earned for services provided to tenants. Sundry revenues are recognized simultaneously with the services provided to the Company’s tenants. Nonfinancial Assets In February 2017, the FASB issued ASU No. 2017-05 (“ASU 2017-05”) to provide guidance for recognizing gains and losses from the transfer of nonfinancial assets and in-substance nonfinancial assets in contracts with non-customers, unless other specific guidance applies. The standard requires a company to derecognize nonfinancial assets once it transfers control of a distinct nonfinancial asset or distinct in substance nonfinancial asset. Additionally, when a company transfers its controlling interest in a nonfinancial asset, but retains a noncontrolling ownership interest, the company is required to measure any noncontrolling interest it receives or retains at fair value. The guidance requires companies to recognize a full gain or loss on the transaction. The Company adopted ASU 2017-05 in the first quarter of 2018 using the modified retrospective method. This adoption requires the Company to analyze incomplete contracts related to property dispositions previously accounted for under ASC 360-20 and to determine whether such arrangements had any forms of continuing involvement that may have affected the revenue or profit recognition of the transactions, including arrangements with prohibited forms of continuing involvement. The Company evaluated the following incomplete contracts to determine if the revenue recognition pattern was affected by ASU 2017-05: Garza Land Sales On July 1, 2016, the Company acquired 34.6 acres of land located in Austin, Texas known as the Garza Ranch, for a purchase price of $20.6 million. As of December 31, 2018, the Company sold three parcels containing 8.4 acres, 1.7 acres and 6.6 acres to three unaffiliated third parties. Two of the land parcels were sold to third party developers on January 30, 2017 and April 28, 2017 and the third land parcel was sold to a third party on March 16, 2018. In connection with the agreements of sale, the Company entered into a development agreement and related completion guarantee to construct certain infrastructure improvements to the land. These improvement costs were included in the sale price of each land parcel. Due to the completion guarantee, the Company did not transfer control to the buyers of the land parcels and recognition of the sale was deferred until the improvements were substantially complete. The cash received at settlement was recorded in the “Deferred income, gains and rent” caption on the Company’s consolidated balance sheets. During the three-month period ended June 30, 2018, the infrastructure improvements were substantially completed. As a result, the Company transferred control of the land parcels to the buyers and recognized the land sales. Accordingly, during the three-month period ended June 30, 2018, the Company applied the cash proceeds received from the settlements of each parcel and recognized an aggregate $2.8 million gain. During the quarter ended December 31, 2018, the Company recognized an additional $0.2 million gain. The following table details the gain on sale for each land parcel, as of December 31, 2018 (dollars, in thousands): Disposition Date Property/Portfolio Location Number Acres Sales Net Gain March 16, 2018 Garza Ranch - Office Austin, TX 1 6.6 $ 14,571 $ 14,509 $ 1,515 April 28, 2017 Garza Ranch - Multifamily Austin, TX 1 8.4 11,800 11,560 1,311 January 30, 2017 Garza Ranch - Hotel Austin, TX 1 1.7 3,500 3,277 192 Total Dispositions 3 16.7 $ 29,871 $ 29,346 $ 3,018 Based on the facts and circumstances, revenue recognition under ASU 2017-05 coincides with the Company’s conclusion under ASC 360-20, and as a result, no cumulative effect adjustment to the consolidated financial statements was necessary as a result of implementing the guidance for the sale of nonfinancial assets. Marine Piers Sublease Interest Sale On March 15, 2017, the Company sold its sublease interest in the Piers at Penn’s Landing (the “Marine Piers”), which includes leasehold improvements containing 181,900 net rentable square feet, and a marina, located in Philadelphia, Pennsylvania, for an aggregate sales price of $21.4 million. On the closing date, the buyer paid $12.0 million in cash and the Company received cash proceeds of $11.2 million, after closing costs and prorations. The $9.4 million balance of the purchase price is due on (a) January 31, 2020, in the event that the tenant at the Marine Piers does not exercise an option it holds to extend the term of the sublease or (b) January 15, 2024, in the event that the tenant does exercise the option to extend the term of the sublease. In accordance with ASU 2017-05, the Company determined that it is appropriate to recognize the sale of the sublease interest in the Marine Piers and to defer the amount of the pending payment due from the buyer because the Company cannot determine the collectability of the remaining $9.4 million balance due under the purchase and sale agreement. The net book value of the Marine Piers was $4.7 million, resulting in a gain on sale of $6.5 million. The remaining gain on sale of $9.4 million arising from the pending payment will be recognized at the earlier of: (i) the time that the Company determines collection of the deferred payment is probable or (ii) on the second purchase price installment date. Based on the facts and circumstances, revenue recognition under ASU 2017-05 coincides with the Company’s previous conclusion under ASC 360-20, and therefore no restatement of the consolidated financial statements is necessary as a result of implementing the guidance for the sale of nonfinancial assets. Subaru National Training Center On December 3, 2015, the Company entered into an agreement to construct an 83,000 square foot build-to-suit service center (the “Subaru NSTC Development”) on land parcels owned by the Company for Subaru as the single tenant. Concurrently, Subaru entered into an 18-year lease for the service center. The lease was classified as a direct finance lease within the “Other assets” caption on the consolidated balance sheets. The lease contained a purchase option, which allowed Subaru to purchase the property at the commencement of the lease, or five years subsequent to inception, at depreciated cost. During the third quarter of 2018, the lease commenced and Subaru exercised its purchase option for the Subaru NSTC Development. In connection with the lease, the Company recognized $1.6 million in interest income during the twelve months ended December 31, 2018, in accordance with accounting guidance for direct finance leases. On December 21, 2018, the Company sold its interest in the Subaru NSTC Development to Subaru for a gross sales price of $45.3 million. The Company received $44.9 million in cash proceeds, after closing costs and prorations.
Income Taxes	Income Taxes Parent Company The Parent Company has elected to be treated as a REIT under Sections 856 through 860 of the Internal Revenue Code of 1986, as amended (the “Code”). In order to continue to qualify as a REIT, the Parent Company is required to, among other things, distribute at least 90% of its annual REIT taxable income to its shareholders and meet certain tests regarding the nature of its income and assets. As a REIT, the Parent Company is not subject to federal and state (in states that follow federal rules) income taxes with respect to the portion of its income that meets certain criteria and is distributed annually to its shareholders. Accordingly, a nominal provision for federal and state (as applicable) income taxes is included in the accompanying consolidated financial statements with respect to the operations of the Parent Company. The Parent Company intends to continue to operate in a manner that allows it to meet the requirements for taxation as a REIT. If the Parent Company fails to qualify as a REIT in any taxable year, it will be subject to federal and state (as applicable) income taxes and may not be able to qualify as a REIT for the four subsequent tax years. The Parent Company is subject to certain local income taxes. Provision for federal income taxes is recorded in the income tax provision line item and state and local income taxes have been included in operating expenses in the Parent Company’s consolidated statements of operations. The tax basis of the Parent Company’s assets was $3.3 billion and $3.1 billion for the years ended December 31, 2018 and December 31, 2017, respectively. The Parent Company is subject to a 4% federal excise tax if sufficient taxable income is not distributed within prescribed time limits. The excise tax equals 4% of the annual amount, if any, by which the sum of (a) 85% of the Parent Company’s ordinary income and (b) 95% of the Parent Company’s net capital gain exceeds cash distributions and certain taxes paid by the Parent Company. No excise tax was incurred in 2018, 2017 or 2016. The Parent Company has elected to treat several of its subsidiaries as taxable REIT subsidiaries (each a “TRS”). A TRS is subject to federal, state and local income tax. In general, a TRS may perform non-customary services for tenants, hold assets that the Parent Company, as a REIT, cannot hold directly and generally may engage in any real estate or non-real estate related business. The Company’s taxable REIT subsidiaries did not have significant tax provisions or deferred income tax items as of December 31, 2018 and December 31, 2017. During January 2017, the Company placed into service the hotel operations at FMC Tower. In order for the income from hotel property investments to constitute “ rents from real property Legislation commonly known as the Tax Cuts and Jobs Act (the “TCJA”) was signed into law on December 22, 2017. The TCJA makes significant changes to the U.S. federal income tax rules for taxation of individuals and corporations (including REITs), generally effective for taxable years beginning after December 31, 2017. Operating Partnership In general, the Operating Partnership is not subject to federal and state income taxes, and accordingly, no provision for income taxes has been made in the accompanying consolidated financial statements. The partners of the Operating Partnership are required to include their respective share of the Operating Partnership’s profits or losses in their respective tax returns. The Operating Partnership’s tax returns and the amount of allocable partnership profits and losses are subject to examination by federal and state taxing authorities. If such examination results in changes to the Operating Partnership profits or losses, then the tax liability of the partners would be changed accordingly. The tax basis of the Operating Partnership’s assets was $3.3 billion and $3.1 billion for the years ended December 31, 2018 and December 31, 2017, respectively. The Operating Partnership may elect to treat a subsidiary REIT under Sections 856 through 860 of the Code, if applicable. Each subsidiary REIT would be required to meet the requirements for treatment as a REIT under Sections 856 through 860 of the Code. If a subsidiary REIT fails to qualify as a REIT in any taxable year, that subsidiary REIT would be subject to federal and state income taxes and would not be able to qualify as a REIT for the four subsequent taxable years. Also, each subsidiary REIT would be subject to certain local income taxes. The Operating Partnership has elected to treat several of its subsidiaries as TRSs, which are subject to federal, state and local income tax. The Company accounts for income taxes using the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective income tax bases, and for net operating loss, capital loss and tax credit carryforwards. The deferred tax assets and liabilities are measured using the enacted income tax rates in effect for the year in which those temporary differences are expected to be realized or settled. The effect on the deferred tax assets and liabilities from a change in tax rates is recognized in earnings in the period when the new rate is enacted. However, deferred tax assets are recognized only to the extent that it is more likely than not that they will be realized based on consideration of all available evidence, including the future reversals of existing taxable temporary differences, future projected taxable income and tax planning strategies. Valuation allowances are provided if, based upon the weight of the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.
Earnings Per Share	Earnings Per Share Basic earnings per share (“EPS”) is computed by dividing net income available to common shareholders, as adjusted for unallocated earnings, if any, of certain securities, by the weighted average number of common shares outstanding during the year. Diluted EPS reflects the potential dilution that could occur from common shares issuable in connection with awards under share-based compensation plans, including upon the exercise of stock options, and conversion of the noncontrolling interests in the Operating Partnership. Anti-dilutive shares are excluded from the calculation. Earnings Per Unit Basic earnings per unit is computed by dividing net income available to common unitholders, as adjusted for unallocated earnings, if any, of certain securities issued by the Operating Partnership, by the weighted average number of common unit equivalents outstanding during the year. Diluted earnings per unit reflects the potential dilution that could occur from units issuable in connection with awards under share-based compensation plans, including upon the exercise of stock options. Anti-dilutive units are excluded from the calculation.
Share-Based Compensation Plans	Share-Based Compensation Plans The Parent Company maintains a shareholder-approved equity-incentive plan known as the Amended and Restated 1997 Long-Term Incentive Plan (the “1997 Plan”). The 1997 Plan is administered by the Compensation Committee of the Parent Company’s Board of Trustees. Under the 1997 Plan, the Compensation Committee is authorized to award equity and equity-based awards, including incentive stock options, non-qualified stock options, restricted shares and performance-based shares. On May 18, 2017, an additional 2,663,886 awards were authorized for issuance, bringing the total authorized awards to 6,500,000. As of December 31, 2018, 429,434 awards had been granted, 1,295,740 awards were cancelled as a result of stock options that expired during 2018, leaving 7,366,306 awards available for future issuance under the 1997 Plan, which included 964,359 awards for options and share appreciation rights. The Company incurred share-based compensation expense of $7.6 million during 2018, of which $1.6 million was capitalized as part of the Company’s review of employee salaries eligible for capitalization. The Company incurred share-based compensation expense of $6.3 million and $5.6 million during 2017 and 2016, of which $1.2 million and $1.0 million, respectively, were also capitalized. The expensed amounts are included in general and administrative expense on the Company’s consolidated income statement in the respective periods.
Comprehensive Income	Comprehensive Income Comprehensive income is recorded in accordance with the provisions of the accounting standard for comprehensive income. The accounting standard establishes standards for reporting comprehensive income and its components in the financial statements. Comprehensive income includes the effective portions of changes in the fair value of derivatives.
Accounting for Derivative Instruments and Hedging Activities	Accounting for Derivative Instruments and Hedging Activities The Company accounts for its derivative instruments and hedging activities in accordance with the accounting standard for derivative and hedging activities. The accounting standard requires the Company to measure every derivative instrument (including certain derivative instruments embedded in other contracts) at fair value and record them on the balance sheet as either an asset or liability. See disclosures below related to the accounting standard for fair value measurements and disclosures. For derivatives designated as cash flow hedges, the effective portions of changes in the fair value of the derivative are reported in other comprehensive income while the ineffective portions are recognized in earnings. The Company actively manages its ratio of fixed-to-floating rate debt. To manage its fixed and floating rate debt in a cost-effective manner, the Company, from time to time, enters into interest rate swap agreements as cash flow hedges, under which it agrees to exchange various combinations of fixed and/or variable interest rates based on agreed upon notional amounts.
Fair Value Measurements	Fair Value Measurements The Company estimates the fair value of its derivatives in accordance with the accounting standard for fair value measurements and disclosures. The accounting standard defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. It also establishes a fair value hierarchy which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value. Financial assets and liabilities recorded on the consolidated balance sheets are categorized based on the inputs to the valuation techniques as follows: • Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access; • Level 2 inputs are inputs, other than quoted prices included in Level 1, which are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability (other than quoted prices), such as interest rates, foreign exchange rates, and yield curves that are observable at commonly quoted intervals; and • Level 3 inputs are unobservable inputs for the asset or liability, which is typically based on an entity’s own assumptions, as there is little if any, related market activity or information. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability. Non-financial assets and liabilities recorded at fair value on a non-recurring basis include non-financial assets and liabilities measured at fair value in a purchase price allocation and the impairment. The fair values assigned to the Company's purchase price allocations primarily utilize Level 3 inputs. The fair value assigned to the long-lived assets and equity method investments for which there was impairment recorded utilize Level 3 inputs.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In November 2018, the FASB issued ASU No. 2018-19, which clarifies that operating lease receivables are not within the scope of ASC 326-20 and should instead be accounted for under the new leasing standard, ASC 842. The amendments in this update are effective for public business entities for fiscal years beginning after December 15, 2019. The Company has evaluated the impact of this new guidance and determined that it will have an immaterial impact on its consolidated financial statements. In June 2018, the FASB issued ASU No. 2018-07 that aligns the accounting for share-based payment awards issued to employees and nonemployees. Under previously issued GAAP guidance, the accounting for nonemployee share-based payments differed from that applied to employee awards, particularly with regard to the measurement date and the impact of performance conditions. Under the revised guidance, the existing employee guidance will apply to nonemployee share-based transactions (as long as the transaction is not effectively a form of financing), with the exception of specific guidance related to the attribution of compensation cost. The cost of nonemployee awards will continue to be recorded as if the grantor had paid cash for the goods or services. In addition, the contractual term will be able to be used in lieu of an expected term in the option-pricing model for nonemployee awards. Changes to the accounting for nonemployee awards include: • Equity-classified share-based payment awards issued to nonemployees will now be measured on the grant date, instead of the previous requirement to remeasure the awards through the performance completion date. • Compensation cost associated with the award will be recognized when achievement of the performance condition is probable, rather than upon achievement of the performance condition. • The current requirement to reassess the classification (equity or liability) for nonemployee awards upon vesting will be eliminated, except for awards in the form of convertible instruments. • The revised guidance also clarifies that any share-based payment awards issued to customers should be evaluated under ASC 606, Revenue from Contracts with Customers. The amendments in this update are effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. Early adoption is permitted, but no earlier than an entity’s adoption date of Topic 606. Adoption of this ASU has no impact on the Company’s consolidated financial statements. In August 2017, the FASB issued ASU No. 2017-12 to simplify the application of hedge accounting guidance and improve the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. In addition, ASU 2017-12 requires an entity to present the earnings effect of the hedging instrument in the same income statement line item in which the earnings effect of the hedged item is reported. The transition guidance provides companies with the option of early adopting the new standard using a modified retrospective transition method in any interim period after issuance of the update or requires adoption for fiscal years beginning after December 15, 2018. This adoption method requires companies to recognize the cumulative effect of initially applying the guidance as an adjustment to accumulated other comprehensive income with a corresponding adjustment to the opening balance of retained earnings as of the beginning of the fiscal year that an entity adopts the update. Adoption of this standard has no impact on the Company’s financial statements. In June 2016, the FASB issued guidance that changes how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current incurred loss model with an expected loss approach, resulting in more timely recognition of such losses. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted after December 2018. The Company is in the process of evaluating the impact of this new guidance and determined that the adoption of the guidance will have an impact on the Company’s estimation of its allowance for doubtful accounts. The Company has not quantified the impact that this guidance will have on its consolidated financial statements. Leasing Standard In February 2016, the FASB issued guidance (“ASU-2016-02”) modifying the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for in the same manner as operating leases today. The new standard requires lessors to account for leases using an approach that is substantially equivalent to existing guidance for sales-type leases, direct financing leases and operating leases. The guidance supersedes previously issued guidance under ASC Topic 840 “Leases.” The lease ASU requires the use of the modified retrospective transition method and does not allow for a full retrospective approach. However, it provides two options for application of the modified retrospective transition method: • Under the first option, the ASU requires the application of the standard to all leases that exist at or commence after, January 1, 2017 (the beginning of the earliest comparative period presented in the 2019 financial statements), with a cumulative adjustment to the opening balance of retained earnings on January 1, 2017, for the effect of applying the standard at the date of initial applications, and restatement of the amounts presented prior to January 1, 2019. • Under the second option, an entity may elect a package of practical expedients, which allows for the following: o An entity need not reassess whether any expired or existing contracts are or contain leases; o An entity need not reassess the lease classification for any expired or existing leases; and o An entity need not reassess initial direct costs for any existing leases. This package of practical expedients is available as a single election that must be consistently applied to all existing leases at the date of adoption. Lessors that adopt this package are not expected to reassess expired or existing leases at the date of initial application, which is January 1, 2017, under the ASU. This option enables entities to account for their existing leases for the remainder of the respective lease terms following previous accounting guidance, which eliminates the need to calculate a cumulative adjustment to the opening balance of retained earnings. The Company elected to adopt this practical expedient to implement ASC 842. In addition, there is a practical expedient that allows the Company to use hindsight when determining the lease term and assessing the fair value of right of use assets. After considering its impact, the Company has decided not to elect the hindsight expedient as part of the application of the modified retrospective transition method. The Company did not adopt the hindsight practical expedient. Furthermore, in July 2018, the FASB adopted an amendment to the package of practical expedients that provides an optional transition method to make January 1, 2019 the initial application date of the ASU, rather than January 1, 2017. Entities that elect both the package of practical expedients and the optional transitional method will apply the new lease ASU prospectively, to leases commencing or modified after January 1, 2019, and will not be required to apply the disclosures under the new lease ASU to comparative periods. The Company elected to adopt this practical expedient and will only evaluate leases that commenced or are modified subsequent to January 1, 2019. In January 2018, the FASB issued ASU No. 2018-01 to address the accounting treatment of land easements within the context of ASU No. 2016-02, Leases (Topic 842). ASU 2018-01 provides an optional transition practical expedient to not evaluate under Topic 842 existing or expired land easements that were not previously accounted for as leases under the current leases guidance in Topic 840. An entity that elects this practical expedient should evaluate new or modified land easements under Topic 842 beginning at the date that the entity adopts Topic 842. An entity that does not elect this practical expedient should evaluate all existing or expired land easements in connection with the adoption of the new lease requirements in Topic 842 to assess whether they meet the definition of a lease. The Company adopted this ASU and will evaluate land easements entered into subsequent to January 1, 2019 In July 2018, the FASB issued ASU No. 2018-11, an amendment to the lease ASU that will allow lessors to elect, as a practical expedient, not to allocate the total consideration to lease and nonlease components based on their relative standalone selling prices. This practical expedient will allow lessors to elect a combined single lease component presentation if: (i) the timing and pattern of the revenue recognition of the combined single lease component is the same, and (ii) the related lease component and, the combined single lease component would be classified as an operating lease. Nonlease components that do not meet the criteria of this practical expedient will be accounted for under the new revenue recognition ASU. The Company adopted this practical expedient and has determined that lease and nonlease components pattern of recognition is the same. As result, lease and nonlease components will be disclosed as a single lease component. In December 2018, the FASB issued ASU No. 2018-20, an amendment to the lease ASU that will allow lessors to elect to not evaluate whether certain sales taxes and other similar taxes are lessor costs or lessee costs. Instead, those lessors will account for those costs as if they are lessee costs. A lessor making this election will exclude, from the consideration in the contract and from variable payments not included in the consideration in the contract, all collections from lessees of taxes within the scope of the election and will provide certain disclosures. Lessors will allocate certain variable payments to the lease and nonlease components when the changes in facts and circumstances on which the variable payment is based occur. After the allocation, the amount of variable payments allocated to the lease components will be recognized as income in profit or loss in accordance with Topic 842, while the amount of variable payments allocated to nonlease components will be recognized in accordance with other Topics, such as Topic 606. The Company has elected to adopt this ASU. The guidance is effective on January 1, 2019, with early adoption permitted. The ASU is expected to have the following impact on the Company’s consolidated financial statements: • Under ASC 842 as a lessor, the Company evaluated its leases and determined that the lease and nonlease components have the same timing and pattern of recognition. As a result, all lease revenue and related tenant reimbursement revenue earned by the Company will be reported within the “Rents” caption of its consolidated statement of operations. • Under ASC 842 as lessor, the Company is required to record bad debt expense as a reduction of revenue. The Company’s bad debt expense was previously recorded within the operating expense caption on its consolidated statement of operations. • ASC 842 is expected to impact the Company’s consolidated financial statements as the Company has land lease arrangements for which it is the lessee. Based on the Company’s evaluation, it expects to record lease liabilities and right of use assets in the amount of $22.4 million. Additionally, operating expenses are expected increase because of ground rent expense for certain of its CPI indexed ground leases will be recognized on a straight-line basis under the new guidance. • The Company evaluated a ground lease at one of its real estate ventures and determined that under ASC 842, its equity in income will decrease annually for its share of additional ground rent expense recorded under ASC 842. • The Company will expense additional costs related to leasing efforts under ASC 842 compared to the previous GAAP because certain activities performed by personnel involved in the leasing process will no longer be considered incremental costs to execute a lease agreement. Based on the Company’s analysis, leasing expenses will increase for the year ended December 31, 2019, as internal costs and leasing pursuit costs will be expensed as incurred under ASC 842. • The impact of ASC 842 to the Company’s Real Estate Ventures is similar to the items described above.

Organization of the Parent Co_2

Organization of the Parent Company and The Operating Partnership (Tables)	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Summary of Core Portfolio of Operating Properties and Excludes Development and Redevelopment Properties Under Construction	The Company’s core portfolio of operating properties, as of December 31, 2018, excludes one three Number of Properties Rentable Square Feet Office properties 88 15,609,156 Mixed-use properties 4 646,741 Retail property 1 17,884 Core Properties 93 16,273,781 Development property 1 164,818 Redevelopment properties 3 338,650 The Properties 97 16,777,249

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Schedule of Reclassification	I n accordance with ASC 360, and in response to the SEC’s “Disclosure Update and Simplification” release effective November 5, 2018, the Company reclassified gains and losses resulting from wholly owned real estate dispositions from the “Other income (expense)” section to the “Operating income” section within its consolidated statements of operations. As a result, in the consolidated statements of operations for the years ended December 31, 2018, 2017 and 2016, the Company reclassified the following amounts to the “Operating income” section: Caption 2018 2017 2016 Net gain on disposition of real estate $ 2,932 $ 31,657 $ 116,983 Net gain on sale of undepreciated real estate 3,040 953 9,232 Total gain on sale of real estate $ 5,972 $ 32,610 $ 126,215
Compensation Costs (Including Bonuses and Benefits) Capitalized	During the years ended December 31, 2018, 2017 and 2016, the Company’s internal direct construction costs are comprised entirely of capitalized salaries. The following table shows the amount of compensation costs (including bonuses and benefits) capitalized for the years presented (in thousands): December 31, 2018 2017 2016 Development $ 3,185 $ 4,390 $ 3,182 Redevelopment 968 319 144 Tenant Improvements 2,811 1,354 3,391 Total $ 6,964 $ 6,063 $ 6,717
Summary of Revenue Earned by Reportable Segments	The following is a summary of revenue earned by the Company’s reportable segments (see Note 17, “Segment Information,” Twelve-month period ended December 31, 2018 Philadelphia CBD Pennsylvania Suburbs Metropolitan Washington, D.C. Austin, Texas Other Corporate Total Base rent $ 164,369 $ 118,628 $ 80,858 $ 21,757 $ 8,400 $ (1,964 ) $ 392,048 Straight-line rent 11,867 2,851 (1,577 ) 116 201 (449 ) 13,009 Point of sale 23,528 258 1,062 521 230 - 25,599 Total rents 199,764 121,737 80,343 22,394 8,831 (2,413 ) 430,656 Tenant reimbursements 51,572 14,440 3,519 10,736 2,832 (474 ) 82,625 Termination fees 192 1,435 136 - - - 1,763 Third party management fees, labor reimbursement and leasing 855 25 5,793 5,455 4,951 5,478 22,557 Other income 4,334 642 517 80 143 1,028 6,744 Total revenue $ 256,717 $ 138,279 $ 90,308 $ 38,665 $ 16,757 $ 3,619 $ 544,345 (a) Corporate includes intercompany eliminations necessary to reconcile to consolidated Company totals.
Summary of Gain on Sale for Each Land Parcel	The Company sold the following properties during the twelve-month period ended December 31, 2018 (dollars in thousands): Disposition Date Property/Portfolio Name Location Type Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) December Subaru Camden, NJ Mixed-use 1 83,000 $ 45,300 $ 44,877 $ 2,570 December Rockpoint Herndon, VA Office 8 1,293,197 312,000 262,442 397 June 20 Gibbsboro, NJ Office 1 38,260 2,000 1,850 (35 ) Total 10 1,414,457 $ 359,300 $ 309,169 $ 2,932 (a) During the second quarter of 2018, Subaru exercised its purchase option under the lease agreement for the Subaru NSTC and the sale occurred during the fourth quarter of 2018. See Note 2, “ Summary of Significant Accounting Policies ,” for further discussion of the lease agreement and related revenue recognition. (b) On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment (the “Rockpoint Portfolio”) to a newly-formed joint venture (the “Herndon Innovation Center Metro Portfolio Venture, LLC”) for a gross sales price of $312.0 million. The Company and its partner own 15% and 85% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. The Herndon Innovation Center Metro Portfolio Venture, LLC funded the acquisition with $265.2 million of cash, which was distributed to the Company at closing. After funding its share of closing costs and working capital contributions of $2.2 million and $0.6 million, respectively, the Company received $262.4 million of cash proceeds at settlement. The Company recorded an impairment charge of $56.9 million for the Rockpoint Portfolio during the third quarter of 2018. The Company recorded a $0.4 million gain on sale, which represents an adjustment to estimated closing costs used to determine the impairment charge in the third quarter of 2018. For further information related to this transaction, see the “ Herndon Innovation Center Metro Portfolio Venture, LLC Investment in Unconsolidated Real Estate Ventures The Company sold the following land parcels during the twelve-month period ended December 31, 2018 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale March 16, 2018 Garza Ranch - Office Austin, TX 1 6.6 $ 14,571 $ 14,509 $ 1,515 (a) January 10, 2018 Westpark Land Durham, NC 1 13.1 485 412 22 Total Dispositions 2 19.7 $ 15,056 $ 14,921 $ 1,537 (a) As of March 31, 2018, the Company had not transferred control to the buyer of this land parcel, or two other parcels at this site which were sold during 2017, because of a completion guarantee which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The cash received at settlement was recorded as “Deferred income, gains and rent” on the Company’s consolidated balance sheets. During the three months ended June 30, 2018, the infrastructure improvements were substantially completed, at which time the Company transferred control of the land parcels. As a result, the Company then recognized the sales of the three land parcels during 2018 and recorded an aggregate $2.8 million gain. During the quarter ended December 31, 2018, the Company recognized an additional $0.2 million gain. See Note 2, “Summary of Significant Accounting Policies,” The Company sold the following properties during the twelve-month period ended December 31, 2017 (dollars in thousands): Disposition Date Property/Portfolio Name Location Type Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) on Sale (a) November 22, 2017 11, 14, 15, 17 and 18 Campus Boulevard (Newtown Square) Newtown Square, PA Office 5 252,802 $ 42,000 $ 40,459 $ 19,642 October 31, 2017 630 Allendale Road King of Prussia, PA Office 1 150,000 17,500 16,580 3,605 June 27, 2017 Two, Four A, Four B and Five Eves Drive (Evesham Corporate Center) Marlton, NJ Office 4 134,794 9,700 8,650 (325 ) (b) June 12, 2017 7000 Midlantic Drive Mount Laurel, NJ Retail 1 10,784 8,200 7,714 1,413 March 30, 2017 200, 210 & 220 Lake Drive East (Woodland Falls) Cherry Hill, NJ Office 3 215,465 19,000 17,771 (249 ) (c) March 15, 2017 Philadelphia Marine Center (Marine Piers) Philadelphia, PA Mixed-use 1 181,900 21,400 11,182 6,498 (d) March 13, 2017 11700, 11710, 11720 & 11740 Beltsville Drive (Calverton) Beltsville, MD Office 3 313,810 9,000 8,354 - (e) February 2, 2017 1200 & 1220 Concord Avenue (Concord Airport Plaza) Concord, CA Office 2 350,256 33,100 32,010 551 (f) Total Dispositions 20 1,609,811 $ 159,900 $ 142,720 $ 31,135 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) As of March 31, 2017, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of four properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $1.0 million at March 31, 2017, which reduced the aggregate carrying values of the properties from $10.2 million to their estimated fair value of $9.2 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.00% and 9.25%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs. (c) As of December 31, 2016, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of three properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $7.3 million at December 31, 2016, reducing the aggregate carrying values of the properties from $25.8 million to their estimated fair value of $18.5 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 8.75% and 9.00%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs (d) On March 15, 2017, the Company sold its sublease interest in the Piers at Penn’s Landing (the “Marine Piers”), which includes leasehold improvements containing 181,900 net rentable square feet, and a marina, located in Philadelphia, Pennsylvania for an aggregate sales price of $21.4 million. On the closing date, the buyer paid $12.0 million in cash. The $9.4 million balance of the purchase is due on (a) January 31, 2020, in the event that the tenant at the Marine Piers does not exercise an option it holds to extend the term of the sublease or (b) January 15, 2024, in the event that the tenant does exercise the option to extend the term of the sublease. The Company determined that it is appropriate to account for the sales transaction under the cost recovery method. The Company received cash proceeds of $11.2 million, after closing costs and prorations, and the net book value of the Marine Piers was $4.7 million, resulting in a gain on sale of $6.5 million. The remaining gain on sale of $9.4 million will be recognized on the second purchase price installment date. Prior to its sale, the Marine Piers had been classified as mixed-use within the Company’s property count (e) During the fourth quarter of 2016, the Company recognized a $3.0 million impairment related to these properties. During the first quarter of 2017, there was a price reduction of $1.7 million under the agreement of sale and an additional impairment of $1.7 million was recognized (f) During the fourth quarter of 2016, the Company recognized an $11.5 million impairment related to these properties. This sale was designated as a like-kind exchange under Section 1031 of the Internal Revenue Code (“IRC”) and, as such, the proceeds, totaling $32.0 million after closing costs and prorations, were deposited with a Qualified Intermediary, as defined under the IRC. The proceeds received at closing were recorded as “Other assets” in the Company’s consolidated balance sheets. During the third quarter of 2017, the Company acquired 3000 Market Street in Philadelphia, Pennsylvania using the full balance of the Section 1031 proceeds. See “ Acquisition The Company sold the following land parcels during the twelve-month period ended December 31, 2017 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale September 13, 2017 50 E. Swedesford Square Malvern, PA 1 12.0 $ 7,200 $ 7,098 $ 882 July 18, 2017 Bishop's Gate Mount Laurel, NJ 1 49.5 6,000 5,640 71 (a) April 28, 2017 Garza Ranch - Multi-family Austin, TX 1 8.4 11,800 11,560 - (b) February 15, 2017 Gateway Land - Site C Richmond, VA 1 4.8 1,100 1,043 - (c) January 30, 2017 Garza Ranch - Hotel Austin, TX 1 1.7 3,500 3,277 - (b) Total Dispositions 5 76.4 $ 29,600 $ 28,618 $ 953 (a) During the fourth quarter of 2016, the Company recognized an impairment of $3.0 million. During the second quarter of 2017, the Company recorded a held for sale impairment charge of $0.3 million, reducing the aggregate carrying value of the land parcel from $5.9 million to its estimated fair value less costs to sell of $5.6 million. The fair value measurement is based on pricing in the purchase and sale agreement for the property. As the pricing in the purchase and sale agreement is unobservable, the Company determined that the input utilized to determine fair value for the property falls within Level 3 in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The land parcel was sold on July 18, 2017. (b) The Company has a continuing involvement in this property through a completion guaranty, which requires the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The Company recorded the cash received at settlement as “Deferred income, gains and rent” on the Company’s consolidated balance sheet and the Company will recognize the sale upon completion of infrastructure improvements. (c) During the fourth quarter of 2016, the Company recognized a nominal impairment related to this land parcel. The Company sold the following properties during the twelve-month period ended December 31, 2016 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) on Sale (a) October 13, 2016 620, 640, 660 Allendale Road King of Prussia, PA 3 156,669 $ 12,800 $ 12,014 $ 2,382 September 1, 2016 1120 Executive Plaza Mt. Laurel, NJ 1 95,183 9,500 9,241 (18 ) (b) August 2, 2016 50 East Clementon Road Gibbsboro, NJ 1 3,080 1,100 1,011 (85 ) May 11, 2016 196/198 Van Buren Street (Herndon Metro Plaza I&II) Herndon, VA 2 197,225 44,500 43,412 (752 ) (c) February 5, 2016 2970 Market Street (Cira Square) Philadelphia, PA 1 862,692 354,000 350,150 115,828 February 4, 2016 Och-Ziff Portfolio Various 58 3,924,783 398,100 353,971 (372 ) (d) Total Dispositions 66 5,239,632 $ 820,000 $ 769,799 $ 116,983 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) As of June 30, 2016, the Company determined that the sale of the property was probable and classified this property as held for sale in accordance with applicable accounting standards for long lived assets. At such date, the carrying value of the property exceeded the fair value less the anticipated costs of sale. As a result, the Company recognized a provision for impairment totaling approximately $1.8 million during the three-month period ended June 30, 2016. The fair value measurement was based on the pricing in the purchase and sale agreement for the sale of the property. As the pricing in the purchase and sale agreement is unobservable, the Company determined that the inputs utilized to determine fair value for this property falls within Level 3 in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, "Fair Value Measurements and Disclosures.” The loss on sale represents additional closing costs recognized at closing. (c) 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 (d) 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 The Company sold the following land parcels during the twelve-month period ended December 31, 2016 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale (a) December 2, 2016 Oakland Lot B Oakland, CA 1 0.9 $ 13,750 $ 13,411 $ 9,039 August 19, 2016 Highlands Land Mt. Laurel, NJ 1 2.0 288 284 193 January 15, 2016 Greenhills Land Reading, PA 1 120.0 900 837 - (b) Total Dispositions 3 122.9 $ 14,938 $ 14,532 $ 9,232 (a) Gain on Sale is net of closing and other transaction related costs. (b) The carrying value of the land exceeded the fair value less the anticipated costs of sale as of December 31, 2015. Therefore the Company recognized an impairment loss of $0.3 million during the three-month period ended December 31, 2015. There was no gain or loss recognized on the sale during 2016
Garza Land Sale [Member]
Summary of Gain on Sale for Each Land Parcel	The following table details the gain on sale for each land parcel, as of December 31, 2018 (dollars, in thousands): Disposition Date Property/Portfolio Location Number Acres Sales Net Gain March 16, 2018 Garza Ranch - Office Austin, TX 1 6.6 $ 14,571 $ 14,509 $ 1,515 April 28, 2017 Garza Ranch - Multifamily Austin, TX 1 8.4 11,800 11,560 1,311 January 30, 2017 Garza Ranch - Hotel Austin, TX 1 1.7 3,500 3,277 192 Total Dispositions 3 16.7 $ 29,871 $ 29,346 $ 3,018

Real Estate Investments (Tables

Real Estate Investments (Tables)	12 Months Ended
	Dec. 31, 2018
Real Estate Properties [Line Items]
Gross Carrying Value of Operating Properties	As of December 31, 2018 and 2017, the gross carrying value of the operating properties was as follows (in thousands): December 31, December 31, 2018 2017 Land $ 508,363 $ 492,197 Building and improvements 3,029,427 2,896,113 Tenant improvements 415,529 444,038 Total $ 3,953,319 $ 3,832,348
Schedule of Purchase Price Allocation	The Company utilized a number of sources in making estimates of fair value for purposes of allocating the acquisition values to tangible and intangible assets acquired. The acquisition values have been allocated as follows (in thousands): Quarry Lake II Austin Venture Portfolio Four Tower Bridge Acquisition Date 12/19/2018 12/11/2018 01/05/2018 Building, land and improvements $ 35,120 $ 457,390 $ 20,734 Intangible assets acquired 5,809 76,925 3,144 Below market lease liabilities assumed (1,524 ) (13,769 ) (182 ) Deferred gain (a) - 14,594 - Total unencumbered acquisition value $ 39,405 $ 535,140 $ 23,696 Mortgage debt assumed - at fair value (b) - - (9,940 ) Total encumbered acquisition value $ 39,405 $ 535,140 $ 13,756 Total unencumbered acquisition value 39,405 535,140 23,696 Mortgage debt assumed - at fair value (b) - - (9,940 ) Mortgage debt repaid at settlement (c) - (115,461 ) - Investment in unconsolidated real estate ventures - (14,594 ) (3,502 ) Gain on promoted interest in unconsolidated real estate venture - (28,283 ) - Gain on real estate venture transactions - (103,847 ) (11,633 ) Purchase price reduction for note receivable (d) - (130,742 ) - Net working capital assumed (368 ) (24,865 ) 1,379 Total cash payment at settlement $ 39,037 $ 117,348 $ - Weighted average amortization period of intangible assets - 5.5 years 4.1 years Weighted average amortization period of below market liabilities assumed 3.0 years 4.6 years 4.8 years (a) Represents a deferred gain resulting recognized at settlement, which resulted in a reduction in the acquisition value. (b) The outstanding principal balance on mortgage debt for Four Tower Bridge (c) On December 11, 2018, the Company assumed $115.5 million of mortgage debt which was repaid in full at settlement. (d) Represents a note receivable due from the DRA Austin Venture that represents a purchase price reduction. October 13, 2017 Building and improvements $ 30,583 Construction-in-progress 672 Intangible assets acquired (a) 10,575 Below market lease liabilities assumed (b) (4,055 ) $ 37,775 (a) Weighted average amortization period of 7.9 years. (b) Weighted average amortization period of 7.0 years. July 28, 2017 Building, land and improvements $ 32,004 Intangible assets acquired (a) 2,562 Below market lease liabilities assumed (b) (1,818 ) $ 32,748 (a) Weighted average amortization period of 5.9 years. (b) Weighted average amortization period of 6.0 years.
Schedule of Pro Forma Information	The unaudited pro forma information below summarizes the Company’s combined results of operations for the years ended December 31, 2018 and December 31, 2017, respectively, as though the acquisition of the Austin Venture Portfolio was completed on January 1, 2017. The supplemental pro forma operating data is not necessarily indicative of what the actual results of operations would have been assuming the transaction had been completed as set forth above, nor do they purport to represent the Company’s results of operations for future periods (in thousands, except for per share amounts). December 31, 2018 2017 Pro forma revenue $ 602,713 $ 582,244 Pro forma net income 134,142 115,475 Pro forma net income available to common shareholders 134,142 115,475
Summary of Gain on Sale for Each Land Parcel	The Company sold the following properties during the twelve-month period ended December 31, 2018 (dollars in thousands): Disposition Date Property/Portfolio Name Location Type Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) December Subaru Camden, NJ Mixed-use 1 83,000 $ 45,300 $ 44,877 $ 2,570 December Rockpoint Herndon, VA Office 8 1,293,197 312,000 262,442 397 June 20 Gibbsboro, NJ Office 1 38,260 2,000 1,850 (35 ) Total 10 1,414,457 $ 359,300 $ 309,169 $ 2,932 (a) During the second quarter of 2018, Subaru exercised its purchase option under the lease agreement for the Subaru NSTC and the sale occurred during the fourth quarter of 2018. See Note 2, “ Summary of Significant Accounting Policies ,” for further discussion of the lease agreement and related revenue recognition. (b) On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment (the “Rockpoint Portfolio”) to a newly-formed joint venture (the “Herndon Innovation Center Metro Portfolio Venture, LLC”) for a gross sales price of $312.0 million. The Company and its partner own 15% and 85% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. The Herndon Innovation Center Metro Portfolio Venture, LLC funded the acquisition with $265.2 million of cash, which was distributed to the Company at closing. After funding its share of closing costs and working capital contributions of $2.2 million and $0.6 million, respectively, the Company received $262.4 million of cash proceeds at settlement. The Company recorded an impairment charge of $56.9 million for the Rockpoint Portfolio during the third quarter of 2018. The Company recorded a $0.4 million gain on sale, which represents an adjustment to estimated closing costs used to determine the impairment charge in the third quarter of 2018. For further information related to this transaction, see the “ Herndon Innovation Center Metro Portfolio Venture, LLC Investment in Unconsolidated Real Estate Ventures The Company sold the following land parcels during the twelve-month period ended December 31, 2018 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale March 16, 2018 Garza Ranch - Office Austin, TX 1 6.6 $ 14,571 $ 14,509 $ 1,515 (a) January 10, 2018 Westpark Land Durham, NC 1 13.1 485 412 22 Total Dispositions 2 19.7 $ 15,056 $ 14,921 $ 1,537 (a) As of March 31, 2018, the Company had not transferred control to the buyer of this land parcel, or two other parcels at this site which were sold during 2017, because of a completion guarantee which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The cash received at settlement was recorded as “Deferred income, gains and rent” on the Company’s consolidated balance sheets. During the three months ended June 30, 2018, the infrastructure improvements were substantially completed, at which time the Company transferred control of the land parcels. As a result, the Company then recognized the sales of the three land parcels during 2018 and recorded an aggregate $2.8 million gain. During the quarter ended December 31, 2018, the Company recognized an additional $0.2 million gain. See Note 2, “Summary of Significant Accounting Policies,” The Company sold the following properties during the twelve-month period ended December 31, 2017 (dollars in thousands): Disposition Date Property/Portfolio Name Location Type Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) on Sale (a) November 22, 2017 11, 14, 15, 17 and 18 Campus Boulevard (Newtown Square) Newtown Square, PA Office 5 252,802 $ 42,000 $ 40,459 $ 19,642 October 31, 2017 630 Allendale Road King of Prussia, PA Office 1 150,000 17,500 16,580 3,605 June 27, 2017 Two, Four A, Four B and Five Eves Drive (Evesham Corporate Center) Marlton, NJ Office 4 134,794 9,700 8,650 (325 ) (b) June 12, 2017 7000 Midlantic Drive Mount Laurel, NJ Retail 1 10,784 8,200 7,714 1,413 March 30, 2017 200, 210 & 220 Lake Drive East (Woodland Falls) Cherry Hill, NJ Office 3 215,465 19,000 17,771 (249 ) (c) March 15, 2017 Philadelphia Marine Center (Marine Piers) Philadelphia, PA Mixed-use 1 181,900 21,400 11,182 6,498 (d) March 13, 2017 11700, 11710, 11720 & 11740 Beltsville Drive (Calverton) Beltsville, MD Office 3 313,810 9,000 8,354 - (e) February 2, 2017 1200 & 1220 Concord Avenue (Concord Airport Plaza) Concord, CA Office 2 350,256 33,100 32,010 551 (f) Total Dispositions 20 1,609,811 $ 159,900 $ 142,720 $ 31,135 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) As of March 31, 2017, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of four properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $1.0 million at March 31, 2017, which reduced the aggregate carrying values of the properties from $10.2 million to their estimated fair value of $9.2 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.00% and 9.25%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs. (c) As of December 31, 2016, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of three properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $7.3 million at December 31, 2016, reducing the aggregate carrying values of the properties from $25.8 million to their estimated fair value of $18.5 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 8.75% and 9.00%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs (d) On March 15, 2017, the Company sold its sublease interest in the Piers at Penn’s Landing (the “Marine Piers”), which includes leasehold improvements containing 181,900 net rentable square feet, and a marina, located in Philadelphia, Pennsylvania for an aggregate sales price of $21.4 million. On the closing date, the buyer paid $12.0 million in cash. The $9.4 million balance of the purchase is due on (a) January 31, 2020, in the event that the tenant at the Marine Piers does not exercise an option it holds to extend the term of the sublease or (b) January 15, 2024, in the event that the tenant does exercise the option to extend the term of the sublease. The Company determined that it is appropriate to account for the sales transaction under the cost recovery method. The Company received cash proceeds of $11.2 million, after closing costs and prorations, and the net book value of the Marine Piers was $4.7 million, resulting in a gain on sale of $6.5 million. The remaining gain on sale of $9.4 million will be recognized on the second purchase price installment date. Prior to its sale, the Marine Piers had been classified as mixed-use within the Company’s property count (e) During the fourth quarter of 2016, the Company recognized a $3.0 million impairment related to these properties. During the first quarter of 2017, there was a price reduction of $1.7 million under the agreement of sale and an additional impairment of $1.7 million was recognized (f) During the fourth quarter of 2016, the Company recognized an $11.5 million impairment related to these properties. This sale was designated as a like-kind exchange under Section 1031 of the Internal Revenue Code (“IRC”) and, as such, the proceeds, totaling $32.0 million after closing costs and prorations, were deposited with a Qualified Intermediary, as defined under the IRC. The proceeds received at closing were recorded as “Other assets” in the Company’s consolidated balance sheets. During the third quarter of 2017, the Company acquired 3000 Market Street in Philadelphia, Pennsylvania using the full balance of the Section 1031 proceeds. See “ Acquisition The Company sold the following land parcels during the twelve-month period ended December 31, 2017 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale September 13, 2017 50 E. Swedesford Square Malvern, PA 1 12.0 $ 7,200 $ 7,098 $ 882 July 18, 2017 Bishop's Gate Mount Laurel, NJ 1 49.5 6,000 5,640 71 (a) April 28, 2017 Garza Ranch - Multi-family Austin, TX 1 8.4 11,800 11,560 - (b) February 15, 2017 Gateway Land - Site C Richmond, VA 1 4.8 1,100 1,043 - (c) January 30, 2017 Garza Ranch - Hotel Austin, TX 1 1.7 3,500 3,277 - (b) Total Dispositions 5 76.4 $ 29,600 $ 28,618 $ 953 (a) During the fourth quarter of 2016, the Company recognized an impairment of $3.0 million. During the second quarter of 2017, the Company recorded a held for sale impairment charge of $0.3 million, reducing the aggregate carrying value of the land parcel from $5.9 million to its estimated fair value less costs to sell of $5.6 million. The fair value measurement is based on pricing in the purchase and sale agreement for the property. As the pricing in the purchase and sale agreement is unobservable, the Company determined that the input utilized to determine fair value for the property falls within Level 3 in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The land parcel was sold on July 18, 2017. (b) The Company has a continuing involvement in this property through a completion guaranty, which requires the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The Company recorded the cash received at settlement as “Deferred income, gains and rent” on the Company’s consolidated balance sheet and the Company will recognize the sale upon completion of infrastructure improvements. (c) During the fourth quarter of 2016, the Company recognized a nominal impairment related to this land parcel. The Company sold the following properties during the twelve-month period ended December 31, 2016 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) on Sale (a) October 13, 2016 620, 640, 660 Allendale Road King of Prussia, PA 3 156,669 $ 12,800 $ 12,014 $ 2,382 September 1, 2016 1120 Executive Plaza Mt. Laurel, NJ 1 95,183 9,500 9,241 (18 ) (b) August 2, 2016 50 East Clementon Road Gibbsboro, NJ 1 3,080 1,100 1,011 (85 ) May 11, 2016 196/198 Van Buren Street (Herndon Metro Plaza I&II) Herndon, VA 2 197,225 44,500 43,412 (752 ) (c) February 5, 2016 2970 Market Street (Cira Square) Philadelphia, PA 1 862,692 354,000 350,150 115,828 February 4, 2016 Och-Ziff Portfolio Various 58 3,924,783 398,100 353,971 (372 ) (d) Total Dispositions 66 5,239,632 $ 820,000 $ 769,799 $ 116,983 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) As of June 30, 2016, the Company determined that the sale of the property was probable and classified this property as held for sale in accordance with applicable accounting standards for long lived assets. At such date, the carrying value of the property exceeded the fair value less the anticipated costs of sale. As a result, the Company recognized a provision for impairment totaling approximately $1.8 million during the three-month period ended June 30, 2016. The fair value measurement was based on the pricing in the purchase and sale agreement for the sale of the property. As the pricing in the purchase and sale agreement is unobservable, the Company determined that the inputs utilized to determine fair value for this property falls within Level 3 in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, "Fair Value Measurements and Disclosures.” The loss on sale represents additional closing costs recognized at closing. (c) 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 (d) 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 The Company sold the following land parcels during the twelve-month period ended December 31, 2016 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale (a) December 2, 2016 Oakland Lot B Oakland, CA 1 0.9 $ 13,750 $ 13,411 $ 9,039 August 19, 2016 Highlands Land Mt. Laurel, NJ 1 2.0 288 284 193 January 15, 2016 Greenhills Land Reading, PA 1 120.0 900 837 - (b) Total Dispositions 3 122.9 $ 14,938 $ 14,532 $ 9,232 (a) Gain on Sale is net of closing and other transaction related costs. (b) The carrying value of the land exceeded the fair value less the anticipated costs of sale as of December 31, 2015. Therefore the Company recognized an impairment loss of $0.3 million during the three-month period ended December 31, 2015. There was no gain or loss recognized on the sale during 2016
Held for Sale Properties Included in Continuing Operations [Member]
Real Estate Properties [Line Items]
Summary of Properties Classified as Held for Sale but Which did not Meet the Criteria to be Classified within Discontinued Operations	The following is a summary of properties classified as held for sale but which did not meet the criteria to be classified within discontinued operations at December 31, 2018 (in thousands): Held for Sale Properties December 31, 2018 Pennsylvania Suburbs - Land (a) Other - Land (a) Total ASSETS HELD FOR SALE Real estate investments: Land inventory $ 4,254 $ 7,345 $ 11,599 Total real estate investments 4,254 7,345 11,599 Total assets held for sale, net $ 4,254 $ 7,345 $ 11,599 The following is a summary of properties classified as held for sale at December 31, 2016 but which did not meet the criteria to be classified within discontinued operations at December 31, 2016 (in thousands): Held for Sale Properties Included in Continuing Operations December 31, 2016 Metropolitan D.C. - Office (a) Other Segment - Office (b) Other Segment - Land (c) Total ASSETS HELD FOR SALE Real estate investments: Operating properties $ 21,720 $ 51,871 $ - $ 73,591 Accumulated depreciation (11,935 ) (20,981 ) - (32,916 ) Operating real estate investments, net 9,785 30,890 - 40,675 Land held for development - - 1,043 1,043 Total real estate investments, net 9,785 30,890 1,043 41,718 Total assets held for sale, net $ 9,785 $ 30,890 $ 1,043 $ 41,718 LIABILITIES HELD FOR SALE Other liabilities $ 73 $ 8 $ - $ 81 Total liabilities held for sale $ 73 $ 8 $ - $ 81 (a) As of December 31, 2016, the Company determined that the sale of three office properties in the Metropolitan D.C. segment was probable and classified these properties as held for sale in accordance with applicable accounting standards for long lived assets. At such date, the carrying value of the properties exceeded their fair value less the anticipated costs of sale. As a result, the Company recognized an impairment loss totaling approximately $3.0 million during the three-month period ended December 31, 2016. The Company measured this impairment based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.00% and 10.00%, respectively. The results were comparable to indicative pricing in the market (b) As The Company measured this impairment based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.75% and 9.75%, respectively. The results were comparable to indicative pricing in the market. (c) As of December 31, 2016, the Company determined that the sale of a land parcel in the Other segment was probable and classified the land parcel as held for sale in accordance with applicable accounting standards for long lived assets. At such date, the carrying value of the land approximated the fair value less the anticipated costs of sale and the Company recorded a nominal impairment. The fair value measurement was based on the pricing in the purchase and sale

Investment in Unconsolidated _2

Investment in Unconsolidated Real Estate Ventures (Tables)	12 Months Ended
	Dec. 31, 2018
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures and Share of Real Estate Ventures' Income (Loss)	The Company’s investment in Real Estate Ventures as of December 31, 2018 and 2017, and the Company’s share of the Real Estate Ventures’ income (loss) for the years ended December 31, 2018 and 2017 was as follows (in thousands): Ownership Carrying Amount Company's Share of Real Estate Venture Income (Loss) Real Estate Venture Debt at 100% Current Interest Debt Percentage (a) 2018 2017 2018 2017 2018 2017 Rate Maturity Office Properties Brandywine-AI Venture LLC (b) 50% $ 11,731 $ 43,560 $ (14,559 ) $ (4,465 ) $ 26,111 $ 93,117 4.65% (c) Rockpoint Venture (d) 15% 47,834 - 83 - - - MAP Venture (e) 50% 11,173 15,450 (2,155 ) (3,443 ) 185,000 180,800 L+2.45% Aug 2023 (e) PJP VII 25% 1,100 1,156 157 175 3,777 4,792 L+2.65% Dec 2019 PJP II 30% 663 604 179 72 2,214 2,564 6.12% Nov 2023 PJP VI 25% 125 179 71 38 7,069 7,370 6.08% Apr 2023 DRA (G&I) Austin (f) 50% - 13,972 1,687 (989 ) - 249,481 Four Tower Bridge (g) 65% - 3,032 - 746 - 9,749 Other Brandywine 1919 Ventures (h) 50% 19,897 22,268 253 (194 ) 88,860 88,860 4% Jun 2023 (i) HSRE-BDN I, LLC 50% - 17,671 (358 ) 449 - 110,886 TB-BDN Plymouth Apartments (j) - - - 99 - - Development Properties 4040 Wilson (k) 50% 37,371 37,179 (192 ) (255 ) 57,288 6,664 L+2.75% Dec 2021 51 N Street 70% 21,368 21,212 (137 ) (176 ) - - 1250 First Street Office 70% 17,838 17,867 (260 ) (149 ) - - Seven Tower Bridge (g) 20% - 471 - (214 ) - 14,629 $ 169,100 $ 194,621 $ (15,231 ) $ (8,306 ) $ 370,319 $ 768,912 (a) Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable. (b) See “ Brandywine - AI Venture: Station Square and 7101 Wisconsin Avenu e” and “ Brandywine - AI Venture: Other Than Temporary Impairment” sections below for information discussing activity that occurred during 2018 and 2017 relating to this venture. (c) The debt for these properties is comprised of one fixed rate mortgage: (1) $26.1 million with a 4.65% fixed interest rate due January 1, 2022. On December 28, 2018, the BDN – (d) On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment, known as the Rockpoint Portfolio, to a newly-formed joint venture, known as the Herndon Innovation Center Metro Portfolio Venture, LLC, for a gross sales price of $312.0 million. Rockpoint and the Company own 85% and 15% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. See “ Herndon Innovation Center Metro Portfolio Venture, LLC ” section below for further details. (e) On August 1, 2018, the MAP Venture refinanced its $180.8 million third party debt financing, secured by the buildings of MAP Venture and maturing February 9, 2019, with $185.0 million third party debt financing, also secured by the buildings, bearing interest at LIBOR + 2.45% capped at a total maximum interest of 6.00% and maturing on August 1, 2023. (f) See “ Austin Venture ” section below for information discussing the Company’s purchase of its partner’s entire 50 % interest in the twelve remaining properties within the Austin Venture on December 11, 2018. (g) On January 5, 2018, the Company exchanged its 20% interest in Seven Tower Bridge to acquire the remaining 35% interest in Four Tower Bridge. For further information regarding the accounting of the transaction, see “ Four Tower Bridge Acquisition (h) The basis difference associated with this venture is allocated between cost and the underlying equity in the net assets of the investee and is accounted for as if the entity were consolidated (i.e., allocated to the Company’s relative share of assets and liabilities with an adjustment to recognize equity in earnings for the appropriate depreciation/amortization). (i) On June 26, 2018, each of the Company and its partner, LCOR/Calstrs, provided a $44.4 million mortgage loan to Brandywine 1919 Ventures. As a result, the Company recorded a related-party note receivable of $44.4 million in the “Other assets” caption on its consolidated balance sheets. The loans bear interest at a fixed 4.0% per annum interest rate with a scheduled maturity on June 25, 2023. On June 26, 2018, Brandywine 1919 Ventures used the loan to repay the venture’s then outstanding $88.8 million construction loan, comprised of $88.6 million in principal and $0.2 million of accrued interest. (j) On January 31, 2017, the Company sold its 50% interest in TB-BDN Plymouth Apartments, LP. (k) During the fourth quarter of 2017, 4040 Wilson obtained a secured construction loan with a total borrowing capacity of $150.0 million. The following is a summary of the financial position of the Real Estate Ventures as of December 31, 2018 and December 31, 2017 (in thousands): December 31, 2018 DRA Brandywine-AI evo Other Total Net property $ - $ 47,043 $ - $ 788,940 $ 835,983 Other assets - 11,206 - 148,293 159,499 Other liabilities - 2,002 - 83,679 85,681 Debt, net - 26,020 - 339,687 365,707 Equity (c) - 30,227 - 513,867 544,094 December 31, 2017 DRA Brandywine-AI evo Other Total Net property $ 263,557 $ 158,960 $ 143,990 $ 517,458 $ 1,083,965 Other assets 42,272 24,181 8,563 86,916 161,932 Other liabilities 24,131 4,493 1,648 67,435 97,707 Debt, net 248,700 92,917 110,136 314,667 766,420 Equity (c) 32,998 85,731 40,769 222,272 381,770 (a) On December 11, 2018, the Company acquired DRA’s 50% ownership interest in the DRA Austin Venture for an aggregate purchase price of $535.1 million. See “Austin Venture” (b) On January 10, 2018, HSRE-BDN I, LLC (evo at Cira Centre South) sold the 345-unit student housing tower, its sole operating asset. See “ evo at Cira Disposition (c) 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. The following is a summary of results of operations of the Real Estate Ventures in which the Company had interests as of December 31, 2018 , 2017 and 2016 (in thousands): Twelve-month period ended December 31, 2018 DRA Brandywine-AI evo Other Total Revenue $ 53,476 $ 23,515 $ 163 $ 88,172 $ 165,326 Operating expenses (22,994 ) (10,483 ) (256 ) (48,302 ) (82,035 ) Interest expense, net (9,083 ) (3,478 ) (123 ) (17,090 ) (29,774 ) Depreciation and amortization (19,226 ) (8,991 ) (409 ) (25,200 ) (53,826 ) Provision for impairment - (20,832 ) - - (20,832 ) Loss on extinguishment of debt (356 ) (695 ) - (334 ) (1,385 ) Net income (loss) $ 1,817 $ (20,964 ) $ (625 ) $ (2,754 ) $ (22,526 ) Ownership interest % 50 % 50 % 50 % (a) Company's share of net income (loss) $ 909 $ (10,482 ) $ (313 ) $ (2,038 ) $ (11,924 ) Other-than-temporary impairment (b) - (4,076 ) - - (4,076 ) Basis adjustments and other 778 (1 ) (45 ) 37 769 Equity in income (loss) of Real Estate Ventures $ 1,687 $ (14,559 ) $ (358 ) $ (2,001 ) $ (15,231 ) Twelve-month period ended December 31, 2017 DRA Brandywine-AI evo Other Total Revenue $ 85,500 $ 29,500 $ 12,285 $ 88,986 $ 216,271 Operating expenses (35,997 ) (12,298 ) (3,075 ) (47,970 ) (99,340 ) Interest expense, net (13,985 ) (4,707 ) (4,092 ) (17,429 ) (40,213 ) Depreciation and amortization (34,026 ) (11,428 ) (4,512 ) (28,474 ) (78,440 ) Loss on extinguishment of debt (2,613 ) (811 ) - - (3,424 ) Net income (loss) $ (1,121 ) $ 256 $ 606 $ (4,887 ) $ (5,146 ) Ownership interest % 50 % 50 % 50 % (a) Company's share of net income (loss) $ (560 ) $ 128 $ 303 $ (1,735 ) $ (1,864 ) Other-than-temporary impairment (b) - (4,844 ) - - (4,844 ) Basis adjustments and other (429 ) 251 146 (1,566 ) (1,598 ) Equity in income (loss) of Real Estate Ventures $ (989 ) $ (4,465 ) $ 449 $ (3,301 ) $ (8,306 ) Twelve-month period ended December 31, 2016 DRA Brandywine-AI evo Other Total Revenue $ 85,749 $ 31,047 $ 12,393 $ 85,263 $ 214,452 Operating expenses (37,643 ) (13,654 ) (3,183 ) (48,712 ) (103,192 ) Provision for impairment (c) - (10,476 ) - - (10,476 ) Interest expense, net (15,052 ) (5,825 ) (3,230 ) (16,207 ) (40,314 ) Depreciation and amortization (38,365 ) (12,811 ) (4,512 ) (30,050 ) (85,738 ) Net income (loss) (d) $ (5,311 ) $ (11,719 ) $ 1,468 $ (9,706 ) $ (25,268 ) Ownership interest % 50 % 50 % 50 % (a) Company's share of net income (loss) $ (2,656 ) $ (5,860 ) $ 734 $ (4,719 ) $ (12,501 ) Basis adjustments and other 776 (35 ) 109 148 998 Equity in income (loss) of Real Estate Ventures $ (1,880 ) $ (5,895 ) $ 843 $ (4,571 ) $ (11,503 ) (a) See above table, which discloses the Company’s investment in Real Estate Ventures as of December 31, 2018 and 2017, for the Company’s unconsolidated ownership interests, subject to specified priority allocations of distributable cash, in certain of the Real Estate Ventures. (b) See “ Brandywine - AI Venture: Other Than Temporary Impairment” section below (c) See “ Brandywine - AI Venture: Station Square Impairment” (d) During the year ended December 31, 2016, there were $7.1 million of acquisition deal costs related to the formation of the MAP Venture.
Schedule of Maturities of Long-term Debt	As of December 31, 2018, the Company’s aggregate scheduled principal payments of debt obligations, excluding amortization of discounts and premiums, are as follows (in thousands): 2019 $ 7,595 2020 87,226 2021 15,143 2022 348,832 2023 556,736 Thereafter 1,028,610 Total principal payments 2,044,142 Net unamortized premiums/(discounts) (5,855 ) Net deferred financing costs (10,241 ) Outstanding indebtedness $ 2,028,046
Summary of Gain on Sale for Each Land Parcel	The Company sold the following properties during the twelve-month period ended December 31, 2018 (dollars in thousands): Disposition Date Property/Portfolio Name Location Type Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) December Subaru Camden, NJ Mixed-use 1 83,000 $ 45,300 $ 44,877 $ 2,570 December Rockpoint Herndon, VA Office 8 1,293,197 312,000 262,442 397 June 20 Gibbsboro, NJ Office 1 38,260 2,000 1,850 (35 ) Total 10 1,414,457 $ 359,300 $ 309,169 $ 2,932 (a) During the second quarter of 2018, Subaru exercised its purchase option under the lease agreement for the Subaru NSTC and the sale occurred during the fourth quarter of 2018. See Note 2, “ Summary of Significant Accounting Policies ,” for further discussion of the lease agreement and related revenue recognition. (b) On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment (the “Rockpoint Portfolio”) to a newly-formed joint venture (the “Herndon Innovation Center Metro Portfolio Venture, LLC”) for a gross sales price of $312.0 million. The Company and its partner own 15% and 85% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. The Herndon Innovation Center Metro Portfolio Venture, LLC funded the acquisition with $265.2 million of cash, which was distributed to the Company at closing. After funding its share of closing costs and working capital contributions of $2.2 million and $0.6 million, respectively, the Company received $262.4 million of cash proceeds at settlement. The Company recorded an impairment charge of $56.9 million for the Rockpoint Portfolio during the third quarter of 2018. The Company recorded a $0.4 million gain on sale, which represents an adjustment to estimated closing costs used to determine the impairment charge in the third quarter of 2018. For further information related to this transaction, see the “ Herndon Innovation Center Metro Portfolio Venture, LLC Investment in Unconsolidated Real Estate Ventures The Company sold the following land parcels during the twelve-month period ended December 31, 2018 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale March 16, 2018 Garza Ranch - Office Austin, TX 1 6.6 $ 14,571 $ 14,509 $ 1,515 (a) January 10, 2018 Westpark Land Durham, NC 1 13.1 485 412 22 Total Dispositions 2 19.7 $ 15,056 $ 14,921 $ 1,537 (a) As of March 31, 2018, the Company had not transferred control to the buyer of this land parcel, or two other parcels at this site which were sold during 2017, because of a completion guarantee which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The cash received at settlement was recorded as “Deferred income, gains and rent” on the Company’s consolidated balance sheets. During the three months ended June 30, 2018, the infrastructure improvements were substantially completed, at which time the Company transferred control of the land parcels. As a result, the Company then recognized the sales of the three land parcels during 2018 and recorded an aggregate $2.8 million gain. During the quarter ended December 31, 2018, the Company recognized an additional $0.2 million gain. See Note 2, “Summary of Significant Accounting Policies,” The Company sold the following properties during the twelve-month period ended December 31, 2017 (dollars in thousands): Disposition Date Property/Portfolio Name Location Type Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) on Sale (a) November 22, 2017 11, 14, 15, 17 and 18 Campus Boulevard (Newtown Square) Newtown Square, PA Office 5 252,802 $ 42,000 $ 40,459 $ 19,642 October 31, 2017 630 Allendale Road King of Prussia, PA Office 1 150,000 17,500 16,580 3,605 June 27, 2017 Two, Four A, Four B and Five Eves Drive (Evesham Corporate Center) Marlton, NJ Office 4 134,794 9,700 8,650 (325 ) (b) June 12, 2017 7000 Midlantic Drive Mount Laurel, NJ Retail 1 10,784 8,200 7,714 1,413 March 30, 2017 200, 210 & 220 Lake Drive East (Woodland Falls) Cherry Hill, NJ Office 3 215,465 19,000 17,771 (249 ) (c) March 15, 2017 Philadelphia Marine Center (Marine Piers) Philadelphia, PA Mixed-use 1 181,900 21,400 11,182 6,498 (d) March 13, 2017 11700, 11710, 11720 & 11740 Beltsville Drive (Calverton) Beltsville, MD Office 3 313,810 9,000 8,354 - (e) February 2, 2017 1200 & 1220 Concord Avenue (Concord Airport Plaza) Concord, CA Office 2 350,256 33,100 32,010 551 (f) Total Dispositions 20 1,609,811 $ 159,900 $ 142,720 $ 31,135 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) As of March 31, 2017, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of four properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $1.0 million at March 31, 2017, which reduced the aggregate carrying values of the properties from $10.2 million to their estimated fair value of $9.2 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.00% and 9.25%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs. (c) As of December 31, 2016, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of three properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $7.3 million at December 31, 2016, reducing the aggregate carrying values of the properties from $25.8 million to their estimated fair value of $18.5 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 8.75% and 9.00%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs (d) On March 15, 2017, the Company sold its sublease interest in the Piers at Penn’s Landing (the “Marine Piers”), which includes leasehold improvements containing 181,900 net rentable square feet, and a marina, located in Philadelphia, Pennsylvania for an aggregate sales price of $21.4 million. On the closing date, the buyer paid $12.0 million in cash. The $9.4 million balance of the purchase is due on (a) January 31, 2020, in the event that the tenant at the Marine Piers does not exercise an option it holds to extend the term of the sublease or (b) January 15, 2024, in the event that the tenant does exercise the option to extend the term of the sublease. The Company determined that it is appropriate to account for the sales transaction under the cost recovery method. The Company received cash proceeds of $11.2 million, after closing costs and prorations, and the net book value of the Marine Piers was $4.7 million, resulting in a gain on sale of $6.5 million. The remaining gain on sale of $9.4 million will be recognized on the second purchase price installment date. Prior to its sale, the Marine Piers had been classified as mixed-use within the Company’s property count (e) During the fourth quarter of 2016, the Company recognized a $3.0 million impairment related to these properties. During the first quarter of 2017, there was a price reduction of $1.7 million under the agreement of sale and an additional impairment of $1.7 million was recognized (f) During the fourth quarter of 2016, the Company recognized an $11.5 million impairment related to these properties. This sale was designated as a like-kind exchange under Section 1031 of the Internal Revenue Code (“IRC”) and, as such, the proceeds, totaling $32.0 million after closing costs and prorations, were deposited with a Qualified Intermediary, as defined under the IRC. The proceeds received at closing were recorded as “Other assets” in the Company’s consolidated balance sheets. During the third quarter of 2017, the Company acquired 3000 Market Street in Philadelphia, Pennsylvania using the full balance of the Section 1031 proceeds. See “ Acquisition The Company sold the following land parcels during the twelve-month period ended December 31, 2017 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale September 13, 2017 50 E. Swedesford Square Malvern, PA 1 12.0 $ 7,200 $ 7,098 $ 882 July 18, 2017 Bishop's Gate Mount Laurel, NJ 1 49.5 6,000 5,640 71 (a) April 28, 2017 Garza Ranch - Multi-family Austin, TX 1 8.4 11,800 11,560 - (b) February 15, 2017 Gateway Land - Site C Richmond, VA 1 4.8 1,100 1,043 - (c) January 30, 2017 Garza Ranch - Hotel Austin, TX 1 1.7 3,500 3,277 - (b) Total Dispositions 5 76.4 $ 29,600 $ 28,618 $ 953 (a) During the fourth quarter of 2016, the Company recognized an impairment of $3.0 million. During the second quarter of 2017, the Company recorded a held for sale impairment charge of $0.3 million, reducing the aggregate carrying value of the land parcel from $5.9 million to its estimated fair value less costs to sell of $5.6 million. The fair value measurement is based on pricing in the purchase and sale agreement for the property. As the pricing in the purchase and sale agreement is unobservable, the Company determined that the input utilized to determine fair value for the property falls within Level 3 in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The land parcel was sold on July 18, 2017. (b) The Company has a continuing involvement in this property through a completion guaranty, which requires the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The Company recorded the cash received at settlement as “Deferred income, gains and rent” on the Company’s consolidated balance sheet and the Company will recognize the sale upon completion of infrastructure improvements. (c) During the fourth quarter of 2016, the Company recognized a nominal impairment related to this land parcel. The Company sold the following properties during the twelve-month period ended December 31, 2016 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Properties Rentable Square Feet Sales Price Net Proceeds on Sale Gain/(Loss) on Sale (a) October 13, 2016 620, 640, 660 Allendale Road King of Prussia, PA 3 156,669 $ 12,800 $ 12,014 $ 2,382 September 1, 2016 1120 Executive Plaza Mt. Laurel, NJ 1 95,183 9,500 9,241 (18 ) (b) August 2, 2016 50 East Clementon Road Gibbsboro, NJ 1 3,080 1,100 1,011 (85 ) May 11, 2016 196/198 Van Buren Street (Herndon Metro Plaza I&II) Herndon, VA 2 197,225 44,500 43,412 (752 ) (c) February 5, 2016 2970 Market Street (Cira Square) Philadelphia, PA 1 862,692 354,000 350,150 115,828 February 4, 2016 Och-Ziff Portfolio Various 58 3,924,783 398,100 353,971 (372 ) (d) Total Dispositions 66 5,239,632 $ 820,000 $ 769,799 $ 116,983 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) As of June 30, 2016, the Company determined that the sale of the property was probable and classified this property as held for sale in accordance with applicable accounting standards for long lived assets. At such date, the carrying value of the property exceeded the fair value less the anticipated costs of sale. As a result, the Company recognized a provision for impairment totaling approximately $1.8 million during the three-month period ended June 30, 2016. The fair value measurement was based on the pricing in the purchase and sale agreement for the sale of the property. As the pricing in the purchase and sale agreement is unobservable, the Company determined that the inputs utilized to determine fair value for this property falls within Level 3 in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, "Fair Value Measurements and Disclosures.” The loss on sale represents additional closing costs recognized at closing. (c) 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 (d) 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 The Company sold the following land parcels during the twelve-month period ended December 31, 2016 (dollars in thousands): Disposition Date Property/Portfolio Name Location Number of Parcels Acres Sales Price Net Proceeds on Sale Gain on Sale (a) December 2, 2016 Oakland Lot B Oakland, CA 1 0.9 $ 13,750 $ 13,411 $ 9,039 August 19, 2016 Highlands Land Mt. Laurel, NJ 1 2.0 288 284 193 January 15, 2016 Greenhills Land Reading, PA 1 120.0 900 837 - (b) Total Dispositions 3 122.9 $ 14,938 $ 14,532 $ 9,232 (a) Gain on Sale is net of closing and other transaction related costs. (b) The carrying value of the land exceeded the fair value less the anticipated costs of sale as of December 31, 2015. Therefore the Company recognized an impairment loss of $0.3 million during the three-month period ended December 31, 2015. There was no gain or loss recognized on the sale during 2016
Unconsolidated Real Estate Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Schedule of Maturities of Long-term Debt	As of December 31, 2018, the aggregate principal payments of recourse and non-recourse debt payable to third-parties are as follows (in thousands): 2019 $ 4,998 2020 1,290 2021 58,651 2022 25,277 2023 280,005 Thereafter 98 Total principal payments 370,319 Net deferred financing costs (4,612 ) Outstanding indebtedness $ 365,707
Austin Joint Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Summary of Gain on Sale for Each Land Parcel	The summary of the transaction is as follows (in thousands); October 18, 2017 Gross sales price $ 333,250 Debt principal (150,968 ) Debt prepayment penalties (2,120 ) Closing costs and net prorations (7,420 ) Cash to Austin Venture $ 172,742 Company's ownership interest 50 % Cash to the Company $ 86,371 Cash to Austin Venture $ 172,742 Austin Venture basis of sold properties (92,559 ) Austin Venture gain on sale $ 80,183 Company's ownership interest 50 % Company's share of gain $ 40,092 Company's share of gain $ 40,092 Deferred gain from partial sale 12,072 Gain on real estate venture transactions $ 52,164

Deferred Costs (Assets) (Tables

Deferred Costs (Assets) (Tables)	12 Months Ended
	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure	As of December 31, 2018 and 2017, the Company’s deferred costs (assets) were comprised of the following (in thousands): December 31, 2018 Total Cost Amortization Deferred Costs, net Leasing costs $ 144,831 $ (56,846 ) $ 87,985 Financing costs - Revolving Credit Facility 6,298 (3,208 ) 3,090 Total $ 151,129 $ (60,054 ) $ 91,075 December 31, 2017 Total Cost Accumulated Amortization Deferred Costs, net Leasing costs $ 154,481 $ (59,046 ) $ 95,435 Financing costs - Revolving Credit Facility 3,595 (2,335 ) 1,260 Total $ 158,076 $ (61,381 ) $ 96,695

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets and Liabilities	As of December 31, 2018 and 2017, the Company’s intangible assets were comprised of the following (in thousands): December 31, 2018 Total Cost Accumulated Amortization Intangible Assets, net Intangible assets, net: In-place lease value $ 181,887 $ (53,376 ) $ 128,511 Tenant relationship value $ 9,564 (8,551 ) 1,013 Above market leases acquired $ 4,966 (3,142 ) 1,824 Total intangible assets, net $ 196,417 $ (65,069 ) $ 131,348 Acquired lease intangibles, net: Below market leases acquired $ 49,655 $ (17,872 ) $ 31,783 December 31, 2017 Total Cost Accumulated Amortization Intangible Assets, net Intangible assets, net: In-place lease value $ 108,060 $ (47,003 ) $ 61,057 Tenant relationship value 11,201 (9,275 ) 1,926 Above market leases acquired 4,545 (2,556 ) 1,989 Total intangible assets, net $ 123,806 $ (58,834 ) $ 64,972 Acquired lease intangibles, net: Below market leases acquired $ 36,213 $ (15,939 ) $ 20,274
Summary of Amortization for Intangible Assets and Liabilities	As of December 31, 2018, the Company’s annual amortization for its intangible assets/liabilities, assuming no early lease terminations, are as follows (dollars in thousands): Assets Liabilities 2019 $ 41,968 $ 7,403 2020 28,393 5,707 2021 20,128 4,302 2022 12,791 2,654 2023 9,756 2,094 Thereafter 18,312 9,623 Total $ 131,348 $ 31,783

Debt Obligations (Tables)

Debt Obligations (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Consolidated debt obligations	The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at December 31, 2018 and 2017 (in thousands): December 31, 2018 December 31, 2017 Effective Interest Rate Maturity Date MORTGAGE DEBT: Two Logan Square $ 82,805 $ 84,440 3.98% May 2020 Four Tower Bridge 9,526 - 4.50% (a) Feb 2021 One Commerce Square 120,183 123,667 3.64% Apr 2023 Two Commerce Square 110,518 112,000 4.51% Apr 2023 Principal balance outstanding 323,032 320,107 Plus: fair market value premium (discount), net (1,759 ) (2,325 ) Less: deferred financing costs (404 ) (566 ) Mortgage indebtedness $ 320,869 $ 317,216 UNSECURED DEBT $600 million Unsecured Credit Facility $ 92,500 $ - LIBOR + 1.10% Jul 2022 Seven-Year Term Loan - Swapped to fixed 250,000 250,000 2.87% (b) Oct 2022 $350.0M 3.95% Guaranteed Notes due 2023 350,000 350,000 3.87% Feb 2023 $250.0M 4.10% Guaranteed Notes due 2024 250,000 250,000 4.33% Oct 2024 $450.0M 3.95% Guaranteed Notes due 2027 450,000 450,000 4.03% Nov 2027 $250.0M 4.55% Guaranteed Notes due 2029 250,000 250,000 4.60% Oct 2029 Indenture IA (Preferred Trust I) 27,062 27,062 LIBOR + 1.25% Mar 2035 Indenture IB (Preferred Trust I) - Swapped to fixed 25,774 25,774 3.30% Apr 2035 Indenture II (Preferred Trust II) - Swapped to fixed 25,774 25,774 3.09% Jul 2035 Principal balance outstanding 1,721,110 1,628,610 Plus: original issue premium (discount), net (4,096 ) (4,423 ) Less: deferred financing costs (9,837 ) (10,575 ) Total unsecured indebtedness $ 1,707,177 $ 1,613,612 Total Debt Obligations $ 2,028,046 $ 1,930,828 (a) This loan was assumed upon acquisition of the related property on January 5, 2018. The interest rate reflects the market rate at the time of acquisition. (b) On December 13, 2018, the Company amended and restated its $250.0 million seven-year term loan maturing October 8, 2022. In connection with the terms of the amendment, the credit spread on the term loan decreased from LIBOR plus 1.80% to LIBOR plus 1.25%, reducing the Company’s effective interest rate by 0.55%. Through a series of interest rate swaps, the $250.0 million outstanding balance of the term loan has a fixed interest rate of 2.87%.
Summary of debt repurchases	The following table provides additional information on the Company’s repurchase of $325.0 million in the aggregate principal amount of its outstanding unsecured notes (consisting of the 2018 Notes, as indicated above) during the twelve months ended December 31, 2017 (in thousands). There were no repurchases of unsecured debt during the twelve months ended December 31, 2018 or 2016. Notes Principal Repurchase Amount (a) Loss on Early Extinguishment of Debt (b) 2018 4.95% Notes $ 325,000 $ 330,792 $ (3,933 ) (a) Includes prepayment penalties with respect to the redemption of debt. (b) Includes unamortized balance of the original issue discount and deferred financing costs.
Schedule of Maturities of Long-term Debt	As of December 31, 2018, the Company’s aggregate scheduled principal payments of debt obligations, excluding amortization of discounts and premiums, are as follows (in thousands): 2019 $ 7,595 2020 87,226 2021 15,143 2022 348,832 2023 556,736 Thereafter 1,028,610 Total principal payments 2,044,142 Net unamortized premiums/(discounts) (5,855 ) Net deferred financing costs (10,241 ) Outstanding indebtedness $ 2,028,046

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments With Fair Values Different From Their Carrying Amount	The following are financial instruments for which the Company’s estimates of fair value differ from the carrying amounts (in thousands): December 31, 2018 December 31, 2017 Carrying Amount (a) Fair Value Carrying Amount (a) Fair Value Unsecured notes payable $ 1,288,024 $ 1,262,570 $ 1,286,573 $ 1,314,900 Variable rate debt $ 419,153 $ 402,924 $ 327,039 $ 308,872 Mortgage notes payable $ 320,869 $ 318,515 $ 317,216 $ 304,665 Notes receivable (b) $ 47,771 $ 47,747 $ 3,532 $ 3,605 (a) T he carrying amounts presented in the table above are net of deferred financing costs of $7.9 million and $8.9 million for unsecured notes payable, $5.1 million and $1.3 million for variable rate debt and $0.4 million and $0.6 million for mortgage notes payable as of December 31, 2018 and December 31, 2017, respectively. (b) The inputs to originate the notes receivable are unobservable and, as a result, are categorized as Level 3. The Company determined fair value by calculating the present value of the cash payments to be received through the maturity date of the loans.

Risk Management and Use of De_2

Risk Management and Use of Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following table summarizes the terms and fair values of the Company’s derivative financial instruments as of December 31, 2018 and December 31, 2017. The notional amounts provide an indication of the extent of the Company’s involvement in these instruments at that time but do not represent exposure to credit, interest rate or market risks (amounts presented in thousands). Hedge Product Hedge Type Designation Notional Amount Strike Trade Date Maturity Date Fair value 12/31/2018 12/31/2017 12/31/2018 12/31/2017 Assets Swap Interest Rate Cash Flow (a) $ 250,000 $ 250,000 2.868 % October 8, 2015 October 8, 2022 $ 7,008 $ 5,694 Swap Interest Rate Cash Flow (a) 25,774 25,774 3.300 % December 22, 2011 January 30, 2021 292 25 Swap Interest Rate Cash Flow (a) 25,774 25,774 3.090 % January 6, 2012 October 30, 2019 183 59 $ 301,548 $ 301,548 (a) Hedging unsecured variable rate debt.

Beneficiaries Equity of the P_2

Beneficiaries Equity of the Parent Company (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Earnings Per Share (EPS), Basic and Diluted	The following tables detail the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding): Year ended December 31, 2018 2017 2016 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 137,289 $ 137,289 $ 121,859 $ 121,859 $ 40,501 $ 40,501 Net income attributable to noncontrolling interests (965 ) (965 ) (1,009 ) (1,009 ) (310 ) (310 ) Nonforfeitable dividends allocated to unvested restricted shareholders (369 ) (369 ) (327 ) (327 ) (341 ) (341 ) Distribution to preferred shareholders - - (2,032 ) (2,032 ) (6,900 ) (6,900 ) Preferred share redemption charge - - (3,181 ) (3,181 ) - - Net income attributable to common shareholders $ 135,955 $ 135,955 $ 115,310 $ 115,310 $ 32,950 $ 32,950 Denominator Weighted-average shares outstanding 178,519,748 178,519,748 175,484,350 175,484,350 175,018,163 175,018,163 Contingent securities/Share based compensation - 1,121,744 - 1,323,816 - 992,651 Weighted-average shares outstanding 178,519,748 179,641,492 175,484,350 176,808,166 175,018,163 176,010,814 Earnings per Common Share: Net income attributable to common shareholders $ 0.76 $ 0.76 $ 0.66 $ 0.65 $ 0.19 $ 0.19

Partners Equity of the Operat_2

Partners Equity of the Operating Partnership (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share (EPS), Basic and Diluted	The following tables detail the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding): Year ended December 31, 2018 2017 2016 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 137,289 $ 137,289 $ 121,859 $ 121,859 $ 40,501 $ 40,501 Net income attributable to noncontrolling interests (965 ) (965 ) (1,009 ) (1,009 ) (310 ) (310 ) Nonforfeitable dividends allocated to unvested restricted shareholders (369 ) (369 ) (327 ) (327 ) (341 ) (341 ) Distribution to preferred shareholders - - (2,032 ) (2,032 ) (6,900 ) (6,900 ) Preferred share redemption charge - - (3,181 ) (3,181 ) - - Net income attributable to common shareholders $ 135,955 $ 135,955 $ 115,310 $ 115,310 $ 32,950 $ 32,950 Denominator Weighted-average shares outstanding 178,519,748 178,519,748 175,484,350 175,484,350 175,018,163 175,018,163 Contingent securities/Share based compensation - 1,121,744 - 1,323,816 - 992,651 Weighted-average shares outstanding 178,519,748 179,641,492 175,484,350 176,808,166 175,018,163 176,010,814 Earnings per Common Share: Net income attributable to common shareholders $ 0.76 $ 0.76 $ 0.66 $ 0.65 $ 0.19 $ 0.19
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings Per Share (EPS), Basic and Diluted	The following tables detail the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding): Year ended December 31, 2018 2017 2016 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 137,289 $ 137,289 $ 121,859 $ 121,859 $ 40,501 $ 40,501 Net income attributable to noncontrolling interests (55 ) (55 ) (29 ) (29 ) (15 ) (15 ) Nonforfeitable dividends allocated to unvested restricted unitholders (369 ) (369 ) (327 ) (327 ) (341 ) (341 ) Preferred unit dividends - - (2,032 ) (2,032 ) (6,900 ) (6,900 ) Preferred unit redemption charge - - (3,181 ) (3,181 ) - - Net income attributable to common unitholders $ 136,865 $ 136,865 $ 116,290 $ 116,290 $ 33,245 $ 33,245 Denominator Weighted-average units outstanding 179,959,370 179,959,370 176,964,149 176,964,149 176,523,800 176,523,800 Contingent securities/Share based compensation - 1,121,744 - 1,323,816 - 992,651 Total weighted-average units outstanding 179,959,370 181,081,114 176,964,149 178,287,965 176,523,800 177,516,451 Earnings per Common Partnership Unit: Net income attributable to common unitholders $ 0.76 $ 0.76 $ 0.66 $ 0.65 $ 0.19 $ 0.19

Share Based Compensation, 401_2

Share Based Compensation, 401(k) Plan and Deferred Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Option Activity	Option activity as of December 31, 2018 and changes during the year-ended December 31, 2018 were as follows: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at January 1, 2018 2,238,590 $ 15.67 1.10 Exercised - $ - $ - Forfeited/Expired (1,274,231 ) $ 20.61 Outstanding at December 31, 2018 964,359 $ 9.13 1.25 $ 3,652,903 Vested/Exercisable at December 31, 2018 964,359 $ 9.13 1.25 $ 3,652,903
Company's Restricted Share Activity	The following table summarizes the Company’s restricted share activity during the year-ended December 31, 2018: Shares Weighted Average Grant Date Fair Value Aggregate Intrinsic Value Non-vested at January 1, 2018 455,643 $ 14.95 $ 8,288,146 Granted 220,241 15.71 - Vested (197,344 ) 15.87 5,923 Forfeited (12,101 ) 15.04 23,292 Non-vested at December 31, 2018 466,439 $ 14.93 $ 70,677
Schedule of Restricted Performance Share Units Plan	The table below presents certain information as to unvested RPSU awards. RPSU Grant 2/22/2016 3/1/2017 2/28/2018 Total (Amounts below in shares, unless otherwise noted) Non-vested at January 1, 2018 228,077 172,411 - 400,488 Units Granted - - 209,193 209,193 Units Cancelled (3,354 ) (2,886 ) (3,168 ) (9,408 ) Non-vested at December 31, 2018 224,723 169,525 206,025 600,273 Measurement Period Commencement Date 1/1/2016 1/1/2017 1/1/2018 Measurement Period End Date 12/31/2018 12/31/2019 12/31/2020 Units Granted 231,388 174,854 209,193 Fair Value of Units on Grant Date (in thousands) $ 3,558 $ 3,735 $ 4,276

Distributions (Tables)

Distributions (Tables)	12 Months Ended
	Dec. 31, 2018
Distributions [Abstract]
Schedule of Dividends Payable	The following table provides the tax characteristics of the 2018, 2017 and 2016 distributions paid: Years ended December 31, 2018 2017 2016 (in thousands, except per share amounts) Common Share Distributions: Ordinary income $ 0.55 $ 0.38 $ - Capital gain - 0.26 0.62 Non-taxable distributions 0.17 - - Distributions per share $ 0.72 $ 0.64 $ 0.62 Percentage classified as ordinary income 76.20 % 60.00 % 0.00 % Percentage classified as capital gain 0.00 % 40.00 % 100.00 % Percentage classified as non-taxable distribution 23.80 % 0.00 % 0.00 % Preferred Share Distributions: Total distributions paid $ - $ 2,032 $ 6,900 Percentage classified as ordinary income 0.00 % 60.00 % 0.00 % Percentage classified as capital gain 0.00 % 40.00 % 100.00 % Percentage classified as non-taxable distribution 0.00 % 0.00 % 0.00 %

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2018
Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table details the components of accumulated other comprehensive income (loss) of the Parent Company and the Operating Partnership as of and for the three years ended December 31, 2018 (in thousands): Parent Company Cash Flow Hedges Balance at January 1, 2016 $ (5,192 ) Change in fair market value during year 2,371 Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests (28 ) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,104 Balance at December 31, 2016 $ (1,745 ) Change in fair market value during year 2,948 Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests (34 ) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,230 Balance at December 31, 2017 $ 2,399 Change in fair market value during year 1,478 Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests (39 ) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,191 Balance at December 31, 2018 $ 5,029 Operating Partnership Cash Flow Hedges Balance at January 1, 2016 $ (5,597 ) Change in fair market value during year 2,371 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,104 Balance at December 31, 2016 $ (2,122 ) Change in fair market value during year 2,948 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,230 Balance at December 31, 2017 $ 2,056 Change in fair market value during year 1,478 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,191 Balance at December 31, 2018 $ 4,725

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Real Estate Investments, Net Operating Income and Unconsolidated Real Estate Ventures of Reportable Segments	The following tables provide selected asset information and results of operations of the Company’s reportable segments for the three years ended December 31, 2018, 2017 and 2016 (in thousands): Real estate investments, at cost: December 31, 2018 December 31, 2017 December 31, 2016 Philadelphia CBD $ 1,670,388 $ 1,643,296 $ 1,320,974 Pennsylvania Suburbs 1,004,537 958,796 1,005,446 Metropolitan Washington, D.C. (a) 524,190 978,257 975,987 Austin, Texas (b) 667,698 163,653 146,794 Other 86,506 88,346 137,094 $ 3,953,319 $ 3,832,348 $ 3,586,295 Assets held for sale (c) - - 73,591 Operating Properties $ 3,953,319 $ 3,832,348 $ 3,659,886 Corporate Construction-in-progress $ 150,263 $ 121,188 $ 297,462 Land held for development (d) $ 86,401 $ 98,242 $ 150,970 Prepaid leasehold interests in land held for development, net $ 39,999 $ - $ - (a) On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment, known as the Rockpoint Portfolio, to the Herndon Innovation Center Metro Portfolio Venture, LLC for a gross sales price of $312.0 million. The Company and its partner own 15% and 85% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. The Herndon Innovation Center Metro Portfolio Venture, LLC funded the acquisition with $265.2 million of cash, which was distributed to the Company at closing. After funding its share of closing costs and working capital contributions of $2.2 million and $0.6 million, respectively, the Company received $262.4 million of cash proceeds at settlement. For further information related to this transaction, see the “ Herndon Innovation Center Metro Portfolio Venture, LLC Investment in Unconsolidated Real Estate Ventures (b) On December 11, 2018, the Company acquired from DRA Advisors its 50% ownership interest in the G&I Austin Office LLC real estate venture for an aggregate purchase price of $535.1 million. The DRA Austin Venture owned twelve office properties containing an aggregate 1,570,123 square feet, located in Austin, Texas. As a result of the acquisition, the Company acquired complete ownership of the Austin Venture Portfolio. For further information related to this transaction, see the “ Acquisitions” Real Estate Investments (c) As of December 31, 2016, three office properties in the Metropolitan Washington, D.C. segment and two office properties in the Other segment were classified as held for sale in accordance with applicable accounting standards for long-lived assets. See the “ 2016 ” section of Note 3, “Real Estate Investments,” for further information. (d) As of December 31, 2018, the Company classified 37.9 acres of land held for development , comprised of 2.7 acres and 35.2 acres, located in its Pennsylvania Suburbs segment and Other segment, respectively, as held for sale in accordance with applicable accounting standards for long lived assets. See Note 3 , “Real Estate Investments,” for further information. As of December 31, 2017, the Company classified 13.1 acres of land held for development located in its Other segment as held for sale in accordance with applicable accounting standards for long lived assets. (e) As of December 31, 2018, this caption comprised leasehold interests in prepaid 99-year ground leases at 3025 and 3001-3003 JFK Boulevard, in Philadelphia, Pennsylvania. See Note 3, “Real Estate Investments Years ended December 31, 2018 2017 2016 Total revenue Operating expenses (a) Net operating income (loss) Total revenue Operating expenses (a) Net operating income Total revenue Operating expenses (a) Net operating income Philadelphia CBD $ 256,717 $ (99,449 ) $ 157,268 $ 226,673 $ (88,818 ) $ 137,855 $ 200,245 $ (78,708 ) $ 121,537 Pennsylvania 138,279 (49,357 ) 88,922 139,785 (47,769 ) 92,016 144,338 (49,208 ) 95,130 Metropolitan 90,308 (34,072 ) 56,236 92,024 (35,014 ) 57,010 99,781 (39,036 ) 60,745 Austin, Texas 38,665 (16,739 ) 21,926 34,301 (15,456 ) 18,845 34,585 (13,222 ) 21,363 Other 16,757 (11,888 ) 4,869 18,347 (11,749 ) 6,598 39,359 (23,204 ) 16,155 Corporate 3,619 (6,518 ) (2,899 ) 9,363 (7,193 ) 2,170 7,155 (6,070 ) 1,085 Operating $ 544,345 $ (218,023 ) $ 326,322 $ 520,493 $ (205,999 ) $ 314,494 $ 525,463 $ (209,448 ) $ 316,015 (a) Includes property operating expense, real estate taxes and third party management expense. Unconsolidated real estate ventures: Investment in real estate ventures, at equity Equity in income (loss) of real estate venture As of Years ended December 31, December 31, 2018 December 31, 2017 December 31, 2016 2018 2017 2016 Philadelphia CBD $ 19,897 $ 39,939 $ 48,691 $ (105 ) $ 255 $ (686 ) Pennsylvania Suburbs - 3,503 15,421 - 631 748 Metropolitan Washington, D.C. (a) 136,142 119,817 141,786 (15,065 ) (5,044 ) (6,293 ) MAP Venture (b) 11,173 15,450 20,893 (2,155 ) (3,443 ) (4,218 ) Other 1,888 1,939 1,654 407 285 814 Austin, Texas (c) - 13,973 52,886 1,687 (990 ) (1,868 ) Total $ 169,100 $ 194,621 $ 281,331 $ (15,231 ) $ (8,306 ) $ (11,503 ) (a) On December 20, 2018, the Company formed a joint venture with Rockpoint. See footnote (a) to the “Real estate investments, at cost” (b) The MAP Venture represents a joint venture formed between the Company and MAP Ground Lease Holdings LLC, an affiliate of Och-Ziff Capital Management Group, LLC, on February 4, 2016. The MAP Venture’s business operations, including properties in Richmond, Virginia; Metropolitan Washington, D.C.; New Jersey/Delaware and Pennsylvania Suburbs, are centrally managed with the results reported to management of the Company on a consolidated basis. As a result, the investment in the MAP Venture is separately presented. All other unconsolidated real estate ventures are managed consistently with the Company’s regional segments. (c) See footnote (b) to the “Real estate investments, at cost” table above for further information regarding this transaction.
Reconciliation of Consolidated Net Income (Loss) to Consolidated NOI	The following is a reconciliation of consolidated net income (loss), as defined by GAAP, to consolidated NOI, (in thousands): Years Ended December 31, 2018 2017 2016 Net income $ 137,289 $ 121,859 $ 40,501 Plus: Interest expense 78,199 81,886 84,708 Interest 2,498 2,435 2,696 Interest expense - financing obligation - - 679 Depreciation and amortization 174,259 179,357 189,676 General and administrative expenses 27,802 28,538 26,596 Equity in loss of Real Estate Ventures 15,231 8,306 11,503 Provision for impairment 71,707 3,057 40,517 Loss on early extinguishment of debt 105 3,933 66,590 Less: Interest income 4,703 1,113 1,236 Income tax (provision) benefit (423 ) 628 - Net gain on disposition of real estate 2,932 31,657 116,983 Net gain on sale of undepreciated real estate 3,040 953 9,232 Net gain on real estate venture transactions 142,233 80,526 20,000 Gain on promoted interest in unconsolidated real estate venture 28,283 - - Consolidated net operating income $ 326,322 $ 314,494 $ 316,015

Operating Leases (Tables)

Operating Leases (Tables)	12 Months Ended
	Dec. 31, 2018
Leases Operating [Abstract]
Operating Leases Future Minimum Payments Receivable	The Company leases properties to tenants under operating leases with various expiration dates extending to 2082. Minimum future rentals on non-cancelable leases at December 31, 2018 are as follows (in thousands): Year Minimum Rent 2019 $ 392,058 2020 372,619 2021 349,160 2022 304,445 2023 277,388 Thereafter 1,265,810

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Minimum Future Rental Payments on Non-cancelable Leases	Minimum future rental payments on non-cancelable leases at December 31, 2018 are as follows (in thousands): Year Minimum Rent 2019 $ 1,222 2020 1,222 2021 1,222 2022 1,222 2023 1,222 Thereafter 55,689 Total $ 61,799

Summary of Quarterly Results (T

Summary of Quarterly Results (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following is a summary of quarterly financial information as of and for the years ended December 31, 2018 and 2017 (in thousands, except per share data): Brandywine Realty Trust 1st 2nd 3rd 4th Quarter Quarter Quarter Quarter 2018 Total revenue $ 136,358 $ 133,786 $ 134,998 $ 139,203 (b) Net income (loss) 44,705 13,136 (43,262 ) (a) 122,710 (c) Net income (loss) allocated to Common Shares 44,215 12,920 (43,003 ) 121,823 Basic earnings (loss) per Common Share $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 Diluted earnings (loss) per Common Share $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 2017 Total revenue $ 130,920 $ 127,791 $ 128,438 $ 133,344 Net income 21,271 7,698 19,046 73,844 Net income allocated to Common Shares 19,278 4,092 18,803 73,137 Basic earnings per Common Share $ 0.11 $ 0.02 $ 0.11 $ 0.42 Diluted earnings per Common Share $ 0.11 $ 0.02 $ 0.11 $ 0.41 The summation of quarterly earnings per share amounts does not necessarily equal the full year amounts due to rounding. (a) The decrease in third quarter net income primarily relates to a $56.9 million impairment charge which related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, “Real Estate Investments,” (b) The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, “Real Estate Investments,” for further information on this transaction. (c) The increase in net income for the fourth quarter primarily relates to gains of $103.8 million and $28.3 million, recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, "Real Estate Investments." Brandywine Operating Partnership, L.P. 1st 2nd 3rd 4th Quarter Quarter Quarter Quarter 2018 Total revenue $ 136,358 $ 133,786 $ 134,998 $ 139,203 (b) Net income (loss) 44,705 13,136 (43,262 ) (a) 122,710 (c) Net income (loss) attributable to Common Partnership Unitholders 44,586 13,029 (43,362 ) 122,612 Basic earnings (loss) per Common Partnership Unit $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 Diluted earnings (loss) per Common Partnership Unit $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 2017 Total revenue $ 130,920 $ 127,791 $ 128,438 $ 133,344 Net income 21,271 7,698 19,046 73,844 Net income attributable to Common Partnership Unitholders 19,442 4,129 18,961 73,758 Basic earnings per Common Partnership Unit $ 0.11 $ 0.02 $ 0.11 $ 0.42 Diluted earnings per Common Partnership Unit $ 0.11 $ 0.02 $ 0.11 $ 0.41 The summation of quarterly earnings per share amounts does not necessarily equal the full year amounts due to rounding. (a) (a)The decrease in third quarter net income primarily relates to a $56.9 million impairment charge which related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, “Real Estate Investments,” (b) The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, “Real Estate Investments,” (c) The increase in net income for the fourth quarter primarily relates to gains of $103.8 million and $28.3 million, recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, "Real Estate Investments."

Organization of The Parent Co_3

Organization of The Parent Company and The Operating Partnership (Textual) (Details)	12 Months Ended
	Dec. 31, 2018ft²apropertyParcel
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	97
Net Rentable Square Feet	16,777,249
Land Parcel One [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Land Parcel Two [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company
Organization of The Parent Company and The Operating Partnership [Line Items]
Undeveloped Parcels of Land | a	237.4
Undeveloped Land Held for Sale | a	37.9
Area of Additional Undeveloped Parcels of Land With Option to Purchase | a	55.5
Total Potential Development Capacity	14,300,000
Parent Company | Land Parcel One [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company | Land Parcel Two [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company | Held for Sale Properties Included in Continuing Operations [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Total Potential Development Capacity	400,000
Wholly-owned Management Company Subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet	24,800,000
Wholly-owned Management Company Subsidiaries [Member] | Wholly Owned Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet	16,800,000
Wholly-owned Management Company Subsidiaries [Member] | Partially Owned Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net Rentable Square Feet	8,000,000
Development Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	1
Redevelopment Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	3
Leashold Interest Land [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Parcels | Parcel	2
Leashold Interest Land [Member] | Parent Company
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Parcels | Parcel	2
Undeveloped Parcels of Land Held | a	1.8
Brandywine Operating Partnership LP [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	99.40%
BRSCO [Member] | Subsidiaries [Member] | Brandywine Operating Partnership LP [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	100.00%
BMH [Member] | Subsidiaries [Member] | Brandywine Operating Partnership LP [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	100.00%
BPI [Member] | Subsidiaries [Member] | Brandywine Operating Partnership LP [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	100.00%
BBL [Member] | Subsidiaries [Member] | Brandywine Operating Partnership LP [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	100.00%
BPM [Member] | Subsidiaries [Member] | Brandywine Operating Partnership LP [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	100.00%
BBS [Member] | Subsidiaries [Member] | Brandywine Operating Partnership LP [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	100.00%

Organization of The Parent Co_4

Organization of The Parent Company and The Operating Partnership - Summary of Core Portfolio of Operating Properties and Excludes Development and Redevelopment Properties Under Construction (Details)	Dec. 31, 2018ft²property
Real Estate Properties [Line Items]
Number of Properties | property	97
Rentable Square Feet | ft²	16,777,249
Office Properties [Member]
Real Estate Properties [Line Items]
Number of Properties | property	88
Rentable Square Feet | ft²	15,609,156
Mixed-use Properties [Member]
Real Estate Properties [Line Items]
Number of Properties | property	4
Rentable Square Feet | ft²	646,741
Retail Property [Member]
Real Estate Properties [Line Items]
Number of Properties | property	1
Rentable Square Feet | ft²	17,884
Core Properties [Member]
Real Estate Properties [Line Items]
Number of Properties | property	93
Rentable Square Feet | ft²	16,273,781
Development Property [Member]
Real Estate Properties [Line Items]
Number of Properties | property	1
Rentable Square Feet | ft²	164,818
Redevelopment Properties [Member]
Real Estate Properties [Line Items]
Number of Properties | property	3
Rentable Square Feet | ft²	338,650

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Textual) (Details)	Dec. 21, 2018USD ($)	Aug. 23, 2018	May 18, 2017shares	Mar. 15, 2017USD ($)ft²	Jul. 01, 2016USD ($)a	Dec. 31, 2018USD ($)ft²aParcelCustomershares	Jun. 30, 2018USD ($)	Dec. 31, 2016USD ($)Customer	Dec. 31, 2018USD ($)ft²aParcelCustomershares	Dec. 31, 2017USD ($)ft²Customer	Dec. 31, 2016USD ($)Customer	Jan. 01, 2019USD ($)	Dec. 03, 2015ft²
Accounting Policies [Line Items]
Income tax (provision) benefit									$ (423,000)	$ 628,000	$ 0
Increase in operating cash flows									14,334,000	(1,752,000)	(544,000)
Variable interest entity, assets						$ 414,300,000			414,300,000	412,900,000
Variable interest entity, liabilities						254,100,000			254,100,000	250,400,000
Revenue increased by straight-line rent adjustment									10,400,000	24,900,000	26,300,000
Increased revenue due to amortization of deferred rent									1,800,000	2,200,000	2,100,000
Decrease in revenue due to amortization of lease incentives									1,500,000	1,800,000	2,000,000
Lease agreement variable income									0
Third Party Management Accounts Receivable Outstanding						$ 1,500,000			$ 1,500,000
Rentable Square Feet | ft²						1,414,457			1,414,457
Sales Price						$ 359,300,000			$ 359,300,000
Proceeds from the sale of properties									324,090,000	171,860,000	784,331,000
Assets held for sale, net						11,599,000			11,599,000	392,000
Gain (Loss) on Sale									2,932,000	31,657,000	116,983,000
Gross sales value of office property						$ 359,300,000			359,300,000
Proceeds from real estate venture sales									$ 60,346,000	145,416,000	21,022,000
Common shares for future awards | shares						7,366,306			7,366,306
Additional shares authorized for issuance | shares			2,663,886
Total number of shares authorized for issuance | shares			6,500,000
Number of awards granted | shares									429,434
Number of awards cancelled | shares									1,295,740
Share-based compensation expense									$ 7,600,000	6,300,000	5,600,000
Share-based compensation expense, capitalized									$ 1,600,000	$ 1,200,000	$ 1,000,000
Employee Stock Option And Share Appreciation Rights
Accounting Policies [Line Items]
Common shares for future awards | shares						964,359			964,359
Garza Land Acquisition [Member]
Accounting Policies [Line Items]
Area of land acquired (in acres) | a					34.6
Aggregate gain recognized						$ 200,000	$ 2,800,000
Subaru Build-to-Service Center Project [Member]
Accounting Policies [Line Items]
Rentable Square Feet | ft²													83,000
Sales Price	$ 45,300,000
Lease terms													18 years
Purchase option of lease from inception period		5 years
Direct finance lease, interest income									$ 1,600,000
Gross sales value of office property	45,300,000
Proceeds from real estate venture sales	$ 44,900,000
Garza Land Sale [Member] | Garza Land Acquisition [Member]
Accounting Policies [Line Items]
Area of land acquired (in acres) | a					34.6
Gross purchase value of assets					$ 20,600,000
Number of Parcels | Parcel						3			3
Garza Land Sale [Member] | Parcel One [Member] | Garza Land Acquisition [Member]
Accounting Policies [Line Items]
Area of land sold | a						8.4			8.4
Garza Land Sale [Member] | Parcel Two [Member] | Garza Land Acquisition [Member]
Accounting Policies [Line Items]
Area of land sold | a						1.7			1.7
Garza Land Sale [Member] | Parcel Three [Member] | Garza Land Acquisition [Member]
Accounting Policies [Line Items]
Area of land sold | a						6.6			6.6
Garza Land Sale [Member] | Third Party Developers [Member] | Parcel One [Member] | Garza Land Acquisition [Member]
Accounting Policies [Line Items]
Date of parcels sold									Jan. 30, 2017
Garza Land Sale [Member] | Third Party Developers [Member] | Parcel Two [Member] | Garza Land Acquisition [Member]
Accounting Policies [Line Items]
Date of parcels sold									Apr. 28, 2017
Garza Land Sale [Member] | Third Party [Member] | Parcel Three [Member] | Garza Land Acquisition [Member]
Accounting Policies [Line Items]
Date of parcels sold									Mar. 16, 2018
Philadelphia Marine Center (Marine Piers) [Member]
Accounting Policies [Line Items]
Rentable Square Feet | ft²				181,900						181,900
Sales Price				$ 21,400,000						$ 21,400,000
Payment by cash on purchases				12,000,000						12,000,000
Proceeds from the sale of properties				11,200,000						11,200,000
Balance payment on purchase price				$ 9,400,000						$ 9,400,000
Date of second installment payment				Jan. 31, 2020						Jan. 31, 2020
Assets held for sale, net				$ 4,700,000						$ 4,700,000
Gain (Loss) on Sale				6,500,000						6,500,000
Deferred gain on sale				9,400,000						9,400,000
Gross sales value of office property				$ 21,400,000						$ 21,400,000
Customer Concentration Risk [Member] | Rental Revenue [Member]
Accounting Policies [Line Items]
Number of tenant accounted for 10% or more of the Company's rents | Customer						0		0	0	0	0
Unconsolidated Real Estate Ventures [Member]
Accounting Policies [Line Items]
Capitalized interest									$ 0	$ 400,000	$ 1,900,000
Minimum [Member]
Accounting Policies [Line Items]
Buildings and improvements useful life									5 years
Tenant Improvements Useful Lives									1 year
Lease terms						10 years			10 years
Maximum [Member]
Accounting Policies [Line Items]
Buildings and improvements useful life									55 years
Tenant Improvements Useful Lives									16 years
Lease terms						66 years			66 years
ASU 2016-18 [Member]
Accounting Policies [Line Items]
Restricted cash						$ 400,000		$ 700,000	$ 400,000	1,300,000	700,000
Increase in operating cash flows										1,300,000	$ 700,000
ASU No. 2016-02, Leases (Topic 842) [Member] | Scenario Plan [Member]
Accounting Policies [Line Items]
Lease liabilities												$ 22,400,000
Right of use assets												$ 22,400,000
Impairment Charges [Member]
Accounting Policies [Line Items]
Out-of-period error immaterial in current year								$ 1,200,000
General And Administrative Expense [Member]
Accounting Policies [Line Items]
Income tax (provision) benefit										600,000
Income Tax Expense Benefit [Member]
Accounting Policies [Line Items]
Reclassification of net income tax provision out of general and administrative expenses into net income tax provision										$ 600,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Reclassification (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Net gain on disposition of real estate	$ 2,932	$ 31,657	$ 116,983
Net gain on sale of undepreciated real estate	3,040	953	9,232
Total gain on sale of real estate	$ 5,972	$ 32,610	$ 126,215

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Construction-in-Progress (Textual) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Construction in Progress [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	$ 6,964	$ 6,063	$ 6,717
Development [Member]
Construction in Progress [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	3,185	4,390	3,182
Capitalized interest	$ 3,600	$ 3,100	$ 10,900

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Compensation Costs (Including Bonuses and Benefits) Capitalized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Construction in Progress [Line Items]
Salaries including bonuses and benefits, capitalized during the period	$ 6,964	$ 6,063	$ 6,717
Development [Member]
Construction in Progress [Line Items]
Salaries including bonuses and benefits, capitalized during the period	3,185	4,390	3,182
Redevelopment [Member]
Construction in Progress [Line Items]
Salaries including bonuses and benefits, capitalized during the period	968	319	144
Tenant Improvements [Member]
Construction in Progress [Line Items]
Salaries including bonuses and benefits, capitalized during the period	$ 2,811	$ 1,354	$ 3,391

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Impairment or Disposal of Long-Lived Assets (Textual) (Details)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Disposition of assets, holding period	10 years

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Accounts Receivable and Accrued Rent Receivable (Textual) (Details) $ in Thousands	Dec. 31, 2018USD ($)Customer	Dec. 31, 2017USD ($)Customer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	$ 1,653	$ 3,467
Accrued rent receivable, allowance	11,266	13,645
Tenant Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	$ 1,700	$ 3,500
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of tenant accounted for 10% or more of the Company's accounts receivable | Customer	0	0

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Deferred Costs (Textual) (Details)	12 Months Ended
	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Remaining Lease Period - Minimum	1 year
Remaining Lease Period - Maximum	16 years

Summary of Significant Accou_11

Summary of Significant Accounting Policies - Notes Receivable (Textual) (Details) - USD ($) $ in Thousands	Jun. 26, 2018	Dec. 31, 2018		Dec. 31, 2017	Jan. 20, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable		$ 47,800		$ 3,500
Debt, net		$ 365,707		$ 766,420
1919 Ventures [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt, net	$ 44,400
Loan interest rate	4.00%
Mortgage loans scheduled maturity date	Jun. 25, 2023
Ownership percentage	50.00%	50.00%	[1],[2]		50.00%
Note receivable	$ 44,400
[1]	The basis difference associated with this venture is allocated between cost and the underlying equity in the net assets of the investee and is accounted for as if the entity were consolidated (i.e., allocated to the Company’s relative share of assets and liabilities with an adjustment to recognize equity in earnings for the appropriate depreciation/amortization).
[2]	Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable.

Summary of Significant Accou_12

Summary of Significant Accounting Policies - Summary of Revenue Earned by Reportable Segments (Details) - USD ($) $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2018

[1]

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Segment Reporting Revenue Reconciling Item [Line Items]

Total revenue

$ 139,203

$ 134,998

$ 133,786

$ 136,358

$ 133,344

$ 128,438

$ 127,791

$ 130,920

$ 544,345

$ 520,493

$ 525,463

Philadelphia CBD [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Total revenue

256,717

Pennsylvania Suburbs [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Total revenue

138,279

Metropolitan Washington, D.C. [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Total revenue

90,308

Austin, Texas [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Total revenue

38,665

Other [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Total revenue

16,757

Corporate [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Total revenue

3,619

[2]

9,363

7,155

Base Rent [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

392,048

Base Rent [Member] | Philadelphia CBD [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

164,369

Base Rent [Member] | Pennsylvania Suburbs [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

118,628

Base Rent [Member] | Metropolitan Washington, D.C. [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

80,858

Base Rent [Member] | Austin, Texas [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

21,757

Base Rent [Member] | Other [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

8,400

Base Rent [Member] | Corporate [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

[2]

(1,964)

Straight Line Rent [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

13,009

Straight Line Rent [Member] | Philadelphia CBD [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

11,867

Straight Line Rent [Member] | Pennsylvania Suburbs [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

2,851

Straight Line Rent [Member] | Metropolitan Washington, D.C. [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

(1,577)

Straight Line Rent [Member] | Austin, Texas [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

116

Straight Line Rent [Member] | Other [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

201

Straight Line Rent [Member] | Corporate [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

[2]

(449)

Point of Sale [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

25,599

Point of Sale [Member] | Philadelphia CBD [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

23,528

Point of Sale [Member] | Pennsylvania Suburbs [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

258

Point of Sale [Member] | Metropolitan Washington, D.C. [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

1,062

Point of Sale [Member] | Austin, Texas [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

521

Point of Sale [Member] | Other [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

230

Point of Sale [Member] | Corporate [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

[2]

0

Rents [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

430,656

412,333

421,505

Rents [Member] | Philadelphia CBD [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

199,764

Rents [Member] | Pennsylvania Suburbs [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

121,737

Rents [Member] | Metropolitan Washington, D.C. [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

80,343

Rents [Member] | Austin, Texas [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

22,394

Rents [Member] | Other [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

8,831

Rents [Member] | Corporate [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

[2]

(2,413)

Tenant Reimbursements [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

82,625

72,620

70,629

Tenant Reimbursements [Member] | Philadelphia CBD [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

51,572

Tenant Reimbursements [Member] | Pennsylvania Suburbs [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

14,440

Tenant Reimbursements [Member] | Metropolitan Washington, D.C. [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

3,519

Tenant Reimbursements [Member] | Austin, Texas [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

10,736

Tenant Reimbursements [Member] | Other [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

2,832

Tenant Reimbursements [Member] | Corporate [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

[2]

(474)

Termination Fees [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

1,763

$ 2,370

$ 2,339

Termination Fees [Member] | Philadelphia CBD [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

192

Termination Fees [Member] | Pennsylvania Suburbs [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

1,435

Termination Fees [Member] | Metropolitan Washington, D.C. [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

136

Termination Fees [Member] | Austin, Texas [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

0

Termination Fees [Member] | Other [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

0

Termination Fees [Member] | Corporate [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Lease revenue

[2]

0

Third Party Management Fees, Labor Reimbursement and Leasing [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

22,557

Third Party Management Fees, Labor Reimbursement and Leasing [Member] | Philadelphia CBD [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

855

Third Party Management Fees, Labor Reimbursement and Leasing [Member] | Pennsylvania Suburbs [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

25

Third Party Management Fees, Labor Reimbursement and Leasing [Member] | Metropolitan Washington, D.C. [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

5,793

Third Party Management Fees, Labor Reimbursement and Leasing [Member] | Austin, Texas [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

5,455

Third Party Management Fees, Labor Reimbursement and Leasing [Member] | Other [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

4,951

Third Party Management Fees, Labor Reimbursement and Leasing [Member] | Corporate [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

[2]

5,478

Other Income [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

6,744

Other Income [Member] | Philadelphia CBD [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

4,334

Other Income [Member] | Pennsylvania Suburbs [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

642

Other Income [Member] | Metropolitan Washington, D.C. [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

517

Other Income [Member] | Austin, Texas [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

80

Other Income [Member] | Other [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

143

Other Income [Member] | Corporate [Member]

Segment Reporting Revenue Reconciling Item [Line Items]

Service and other revenue

[2]

$ 1,028

[1]

The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, “Real Estate Investments,” for further information on this transaction.

[2]

Corporate includes intercompany eliminations necessary to reconcile to consolidated Company totals.

Summary of Significant Accou_13

Summary of Significant Accounting Policies - Summary of Gain on Sale for Each Land Parcel (Details) $ in Thousands	Mar. 16, 2018USD ($)aParcel	Apr. 28, 2017USD ($)aParcel	Jan. 30, 2017USD ($)aParcel	Dec. 31, 2018USD ($)aParcel	Dec. 31, 2017USD ($)aParcel		Dec. 31, 2016USD ($)aParcel
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Sales Price				$ 359,300
Proceeds from the sale of properties				324,090	$ 171,860		$ 784,331
Gain on Sale				$ 3,040	$ 953		$ 9,232
Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel				2	5		3
Acreage of land | a				19.7	76.4		122.9
Sales Price				$ 15,056	$ 29,600		$ 14,938
Proceeds from the sale of properties				14,921	28,618		14,532
Gain on Sale				$ 1,537	$ 953		$ 9,232	[1]
Garza Ranch - Office [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel	1
Acreage of land | a	6.6
Sales Price	$ 14,571
Proceeds from the sale of properties	14,509
Gain on Sale	$ 1,515
Garza Ranch - Multifamily [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel		1			1
Acreage of land | a		8.4			8.4
Sales Price		$ 11,800			$ 11,800
Proceeds from the sale of properties		11,560			11,560
Gain on Sale		$ 1,311			$ 0	[2]
Garza Ranch - Hotel [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel			1		1
Acreage of land | a			1.7		1.7
Sales Price			$ 3,500		$ 3,500
Proceeds from the sale of properties			3,277		3,277
Gain on Sale			$ 192		$ 0
Garza Ranch [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel				3
Acreage of land | a				16.7
Sales Price				$ 29,871
Proceeds from the sale of properties				29,346
Gain on Sale				$ 3,018
[1]	Gain on Sale is net of closing and other transaction related costs.
[2]	The Company has a continuing involvement in this property through a completion guaranty, which requires the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The Company recorded the cash received at settlement as “Deferred income, gains and rent” on the Company’s consolidated balance sheet and the Company will recognize the sale upon completion of infrastructure improvements.

Summary of Significant Accou_14

Summary of Significant Accounting Policies - Income Taxes (Textual) (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Distributable Income Minimum Percentage	90.00%
Tax Basis of Assets, Cost for Income Tax Purposes	$ 3.3	$ 3.1
Federal excise tax if sufficient taxable income is not distributed within prescribed time limits	4.00%
Excise tax equal to annual amount	4.00%
Excise tax, if sum of ordinary income	85.00%
Excise tax, if Net capital gain exceeds cash distributions and certain taxes paid	95.00%
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Income Tax Contingency [Line Items]
Tax Basis of Assets, Cost for Income Tax Purposes	$ 3.3	$ 3.1

Real Estate Investments - Gross

Real Estate Investments - Gross Carrying Value of Operating Properties (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment, Gross [Abstract]
Land	$ 508,363	$ 492,197
Tenant improvements	415,529	444,038
Operating properties	3,953,319	3,832,348
Total	3,953,319	3,832,348
Building and Improvements [Member]
Property, Plant and Equipment, Gross [Abstract]
Operating properties	$ 3,029,427	$ 2,896,113

Real Estate Investments - Acqui

Real Estate Investments - Acquisitions (Textual) (Details) $ in Thousands		Dec. 19, 2018USD ($)ft²property	Dec. 11, 2018USD ($)ft²property	Jun. 29, 2018USD ($)ft²	Mar. 22, 2018USD ($)	Jan. 05, 2018USD ($)ft²	Oct. 13, 2017USD ($)ft²	Jul. 28, 2017USD ($)ft²	Jul. 01, 2016USD ($)a	Dec. 31, 2018USD ($)ft²property	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)a	Dec. 31, 2017USD ($)a	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)a	Dec. 31, 2018USD ($)ft²property	Dec. 31, 2017USD ($)a	Dec. 31, 2016USD ($)ft²	Nov. 01, 2018USD ($)	Jan. 30, 2017a
Business Acquisition [Line Items]
Number of Properties acquired | property										97										97
Rentable Square Feet | ft²										1,414,457										1,414,457
Proceeds from credit facility borrowings																				$ 455,500	$ 341,000	$ 195,000
Area of Real Estate Property | ft²										16,777,249										16,777,249
Net gain from remeasurement of investment in real estate ventures																				$ 142,233	80,526	20,000
Gain on promoted interest in unconsolidated real estate venture																				28,283	0	0
Prepaid leasehold interests in land held for development, net	[1]									$ 39,999				$ 0	$ 0				$ 0	39,999	0	0
Capitalized transaction costs																				18,407	17,657	16,083
Net income (loss)										$ 121,823	$ (43,003)	$ 12,920	$ 44,215	$ 73,137		$ 18,803	$ 4,092	$ 19,278		136,324	120,850	40,191
Amount funded by corporate funds																				$ 196,625	$ 72,523	$ 20,406
Garza Land Sale [Member]
Business Acquisition [Line Items]
Area of land under agreement to sell | a																								1.7
Office Properties [Member]
Business Acquisition [Line Items]
Number of Properties acquired | property										88										88
Rentable Square Feet | ft²																						5,239,632
Area of Real Estate Property | ft²										15,609,156										15,609,156
Seven Tower Bridge [Member]
Business Acquisition [Line Items]
Ownership percentage	[2],[3]									20.00%										20.00%
Sale of ownership interest percentage						20.00%
Quarry Lake II [Member]
Business Acquisition [Line Items]
Number of Properties acquired | property		1
Rentable Square Feet | ft²		120,559
Gross purchase value of office property		$ 39,500
Capitalized transaction costs		100
Proceeds from credit facility borrowings		39,000
Mortgage debt assumed in connection with acquisition of real estate properties		0
Working capital obtained		368
Aggregate cash payment		39,037
Mortgage debt assumed repaid at settlement		$ 0
Service and other revenue																				$ 100
Net income (loss)																				100
DRA Austin Venture [Member]
Business Acquisition [Line Items]
Number of Properties acquired | property			12
Gross purchase value of office property			$ 535,100
Ownership percentage			50.00%
Area of Real Estate Property | ft²			1,570,123
Mortgage debt assumed in connection with acquisition of real estate properties			$ 0																				$ 115,500
Investment in real estate venture			14,600
Credit settlement for notes receivable provided to venture																							$ 130,700
Working capital obtained			24,865
Cash proceeds for promoted interest in venture			28,300
Net gain from remeasurement of investment in real estate ventures			103,800							$ 103,800
Aggregate cash payment			117,348
Mortgage debt assumed repaid at settlement			115,461
Gain on promoted interest in unconsolidated real estate venture			$ 28,300							$ 28,300
Percentage of ownership interests			50.00%
Service and other revenue																				3,400
Net income (loss)																				$ (1,300)
3025 JFK Boulevard [Member]
Business Acquisition [Line Items]
Lease agreement term				99 years
Prepaid leasehold interests in land held for development, net				$ 15,000
Capitalized transaction costs				300
3025 JFK Boulevard [Member] | Other Assets [Member]
Business Acquisition [Line Items]
Leasehold Valuation Credit				5,600
3001-3003 and 3025 JFK Boulevard [Member]
Business Acquisition [Line Items]
Lease agreement term																				99 years
Leasehold valuation credit applied to development				$ 2,400
Minimum floor area ratio required for realization of credit | ft²				1,200,000
Remaining leasehold valuation credit				$ 3,200
Reimbursable leasehold valuation credit				$ 3,200
3001-3003 JFK Boulevard [Member]
Business Acquisition [Line Items]
Lease agreement term					99 years
Prepaid leasehold interests in land held for development, net					$ 24,600
Capitalized transaction costs					$ 300
Four Tower Bridge [Member]
Business Acquisition [Line Items]
Capitalized transaction costs						$ 100
Ownership percentage						35.00%
Mortgage debt assumed in connection with acquisition of real estate properties						$ 9,940
Working capital obtained						(1,379)
Aggregate cash payment						0
Mortgage debt assumed repaid at settlement						$ 0
Percentage of ownership interest after non-monetary exchange transaction						100.00%
Fair value of unencumbered acquisition related costs, to tangible and intangible assets and liabilities						$ 23,600
Service and other revenue																				$ 2,800
Net income (loss)																				$ 300
Four Tower Bridge [Member] | Conshohocken [Member] | Pennsylvania [Member]
Business Acquisition [Line Items]
Area of Real Estate Property | ft²						86,021
Real estate property debt						$ 9,700
Bulletin Building [Member]
Business Acquisition [Line Items]
Rentable Square Feet | ft²							282,709
Gross purchase value of office property							$ 35,000
Capitalized transaction costs							$ 2,800
Lease agreement term							99 years
Service and other revenue															1,200
Net income (loss)															$ (400)
3000 Market Street [Member]
Business Acquisition [Line Items]
Gross purchase value of office property								$ 32,700
Capitalized transaction costs								700
Service and other revenue																			800
Net income (loss)																			$ (500)
Contractual sale price of real estate acquired								$ 32,000
3000 Market Street [Member] | Office Properties [Member]
Business Acquisition [Line Items]
Area of Real Estate Property | ft²								58,587
Garza Land Acquisition [Member]
Business Acquisition [Line Items]
Area of land acquired (in acres) | a									34.6
Gross purchase value of assets									$ 20,600
Acquisition costs									1,900
Amount funded by corporate funds									$ 20,400
Area of land under agreement to sell | a														9.5	9.5				9.5		9.5
Garza Land Acquisition [Member] | Garza Land Sale [Member]
Business Acquisition [Line Items]
Area of land acquired (in acres) | a									34.6
[1]	As of December 31, 2018, this caption comprised leasehold interests in prepaid 99-year ground leases at 3025 and 3001-3003 JFK Boulevard, in Philadelphia, Pennsylvania. See Note 3, “Real Estate Investments
[2]	On January 5, 2018, the Company exchanged its 20% interest in Seven Tower Bridge to acquire the remaining 35% interest in Four Tower Bridge. For further information regarding the accounting of the transaction, see “ Four Tower Bridge Acquisition
[3]	Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable.

Real Estate Investments - Purch

Real Estate Investments - Purchase Price Allocation (Details) - USD ($) $ in Thousands		Dec. 19, 2018	Dec. 11, 2018	Jan. 05, 2018	Oct. 13, 2017	Jul. 28, 2017	Nov. 01, 2018
Quarry Lake II [Member]
Business Acquisition [Line Items]
Acquisition Date		Dec. 19, 2018
Building, land and improvements		$ 35,120
Intangible assets acquired		5,809
Below market lease liabilities assumed		(1,524)
Deferred gain		0
Total unencumbered acquisition value		39,405
Mortgage debt assumed - at fair value		0
Total encumbered acquisition value		39,405
Total unencumbered acquisition value		39,405
Mortgage debt repaid at settlement (c)		0
Investment in unconsolidated real estate ventures		0
Gain on promoted interest in unconsolidated real estate venture		0
Gain on real estate venture transactions		0
Purchase price reduction for note receivable		0
Net working capital assumed		(368)
Total cash payment at settlement		$ 39,037
Quarry Lake II [Member] | Below Market Lease [Member]
Business Acquisition [Line Items]
Weighted average amortization period		3 years
DRA Austin Venture [Member]
Business Acquisition [Line Items]
Acquisition Date			Dec. 11, 2018
Building, land and improvements			$ 457,390
Intangible assets acquired			76,925
Below market lease liabilities assumed			(13,769)
Deferred gain			14,594
Total unencumbered acquisition value			535,140
Mortgage debt assumed - at fair value			0				$ (115,500)
Total encumbered acquisition value			535,140
Total unencumbered acquisition value			535,140
Mortgage debt repaid at settlement (c)			(115,461)
Investment in unconsolidated real estate ventures			(14,594)
Gain on promoted interest in unconsolidated real estate venture			(28,283)
Gain on real estate venture transactions			(103,847)
Purchase price reduction for note receivable			(130,742)
Net working capital assumed			(24,865)
Total cash payment at settlement			$ 117,348
DRA Austin Venture [Member] | Intangible Assets Acquired [Member]
Business Acquisition [Line Items]
Weighted average amortization period			5 years 6 months
DRA Austin Venture [Member] | Below Market Lease [Member]
Business Acquisition [Line Items]
Weighted average amortization period			4 years 7 months 6 days
Four Tower Bridge [Member]
Business Acquisition [Line Items]
Acquisition Date				Jan. 5, 2018
Building, land and improvements				$ 20,734
Intangible assets acquired				3,144
Below market lease liabilities assumed				(182)
Deferred gain				0
Total unencumbered acquisition value				23,696
Mortgage debt assumed - at fair value				(9,940)
Total encumbered acquisition value				13,756
Total unencumbered acquisition value				23,696
Mortgage debt repaid at settlement (c)				0
Investment in unconsolidated real estate ventures				(3,502)
Gain on promoted interest in unconsolidated real estate venture				0
Gain on real estate venture transactions				(11,633)
Purchase price reduction for note receivable				0
Net working capital assumed				1,379
Total cash payment at settlement				$ 0
Four Tower Bridge [Member] | Intangible Assets Acquired [Member]
Business Acquisition [Line Items]
Weighted average amortization period				4 years 1 month 6 days
Four Tower Bridge [Member] | Below Market Lease [Member]
Business Acquisition [Line Items]
Weighted average amortization period				4 years 9 months 18 days
Bulletin Building [Member]
Business Acquisition [Line Items]
Building, land and improvements					$ 30,583
Intangible assets acquired	[1]				10,575
Below market lease liabilities assumed	[2]				(4,055)
Total encumbered acquisition value					37,775
Construction-in-progress					$ 672
Bulletin Building [Member] | Intangible Assets Acquired [Member]
Business Acquisition [Line Items]
Weighted average amortization period					7 years 10 months 24 days
Bulletin Building [Member] | Below Market Lease [Member]
Business Acquisition [Line Items]
Weighted average amortization period					7 years
3000 Market Street [Member]
Business Acquisition [Line Items]
Building, land and improvements						$ 32,004
Intangible assets acquired	[3]					2,562
Below market lease liabilities assumed	[4]					(1,818)
Total encumbered acquisition value						$ 32,748
3000 Market Street [Member] | Intangible Assets Acquired [Member]
Business Acquisition [Line Items]
Weighted average amortization period						5 years 10 months 24 days
3000 Market Street [Member] | Below Market Lease [Member]
Business Acquisition [Line Items]
Weighted average amortization period						6 years
[1]	Weighted average amortization period of 7.9 years.
[2]	Weighted average amortization period of 7.0 years.
[3]	Weighted average amortization period of 5.9 years.
[4]	Weighted average amortization period of 6.0 years.

Real Estate Investments - Pur_2

Real Estate Investments - Purchase Price Allocation (Parenthetical) (Details) - USD ($) $ in Thousands	Dec. 11, 2018	Jan. 05, 2018	Oct. 13, 2017	Jul. 28, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Outstanding principal balances on mortgage debt assumed					$ 320,869	$ 317,216
Repayments of mortgage debt assumed					$ 122,180	$ 4,931	$ 357,151
Mortgage Debt Assumed - at Fair Value [Member]
Business Acquisition [Line Items]
Outstanding principal balances on mortgage debt assumed	$ 115,500
Repayments of mortgage debt assumed	$ 115,500
Four Tower Bridge [Member] | Mortgage Debt Assumed - at Fair Value [Member]
Business Acquisition [Line Items]
Outstanding principal balances on mortgage debt assumed		$ 9,700
Four Tower Bridge [Member] | Intangible Assets Acquired [Member]
Business Acquisition [Line Items]
Weighted average amortization period		4 years 1 month 6 days
Four Tower Bridge [Member] | Below Market Lease [Member]
Business Acquisition [Line Items]
Weighted average amortization period		4 years 9 months 18 days
Bulletin Building [Member] | Intangible Assets Acquired [Member]
Business Acquisition [Line Items]
Weighted average amortization period			7 years 10 months 24 days
Bulletin Building [Member] | Below Market Lease [Member]
Business Acquisition [Line Items]
Weighted average amortization period			7 years
3000 Market Street [Member] | Intangible Assets Acquired [Member]
Business Acquisition [Line Items]
Weighted average amortization period				5 years 10 months 24 days
3000 Market Street [Member] | Below Market Lease [Member]
Business Acquisition [Line Items]
Weighted average amortization period				6 years

Real Estate Investments - Pro F

Real Estate Investments - Pro Forma (Details) - DRA Austin Venture [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition Pro Forma Information Nonrecurring Adjustment [Line Items]
Pro forma revenue	$ 602,713	$ 582,244
Pro forma net income	134,142	115,475
Pro forma net income available to common shareholders	$ 134,142	$ 115,475

Real Estate Investments - Summa

Real Estate Investments - Summary of Properties Sold (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2018USD ($)ft²property	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)ft²property
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property		10
Rentable Square Feet | ft²		1,414,457
Sales Price		$ 359,300
Net Proceeds on Sale		309,169
Gain (Loss) on Sale		$ 2,932	$ 31,657	$ 116,983
Mixed-use Properties [Member] | Subaru National Training Center [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property	[1]	1
Rentable Square Feet | ft²	[1]	83,000
Sales Price	[1]	$ 45,300
Net Proceeds on Sale	[1]	44,877
Gain (Loss) on Sale	[1]	$ 2,570
Office Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property				66
Rentable Square Feet | ft²				5,239,632
Sales Price				$ 820,000
Gain (Loss) on Sale	[2]			$ 116,983
Office Properties [Member] | Rockpoint Portfolio [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property	[3]	8
Rentable Square Feet | ft²	[3]	1,293,197
Sales Price	[3]	$ 312,000
Net Proceeds on Sale	[3]	262,442
Gain (Loss) on Sale	[3]	$ 397
Office Properties [Member] | 20 East Clementon Road [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property		1
Rentable Square Feet | ft²		38,260
Sales Price		$ 2,000
Net Proceeds on Sale		1,850
Gain (Loss) on Sale		$ (35)
[1]	During the second quarter of 2018, Subaru exercised its purchase option under the lease agreement for the Subaru NSTC and the sale occurred during the fourth quarter of 2018. See Note 2, “ Summary of Significant Accounting Policies ,” for further discussion of the lease agreement and related revenue recognition.
[2]	Gain/(Loss) on Sale is net of closing and other transaction related costs.
[3]	On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment (the “Rockpoint Portfolio”) to a newly-formed joint venture (the “Herndon Innovation Center Metro Portfolio Venture, LLC”) for a gross sales price of $312.0 million. The Company and its partner own 15% and 85% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. The Herndon Innovation Center Metro Portfolio Venture, LLC funded the acquisition with $265.2 million of cash, which was distributed to the Company at closing. After funding its share of closing costs and working capital contributions of $2.2 million and $0.6 million, respectively, the Company received $262.4 million of cash proceeds at settlement. The Company recorded an impairment charge of $56.9 million for the Rockpoint Portfolio during the third quarter of 2018. The Company recorded a $0.4 million gain on sale, which represents an adjustment to estimated closing costs used to determine the impairment charge in the third quarter of 2018. For further information related to this transaction, see the “ Herndon Innovation Center Metro Portfolio Venture, LLC Investment in Unconsolidated Real Estate Ventures

Real Estate Investments - Sum_2

Real Estate Investments - Summary of Properties Sold (Parenthetical) (Details) $ in Thousands	Dec. 20, 2018USD ($)ft²property	Sep. 30, 2018USD ($)property	Dec. 31, 2018USD ($)ft²	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Schedule Of Equity Method Investments [Line Items]
Area of Real Estate Property | ft²			16,777,249
Net gain on disposition of real estate			$ 2,932	$ 31,657	$ 116,983
Metropolitan Washington, D.C. - Office [Member]
Schedule Of Equity Method Investments [Line Items]
Number of properties contributed to a joint venture | property		8
Impairment on assets held for sale		$ 56,900
Rockpoint Portfolio [Member] | Metropolitan Washington, D.C. - Office [Member]
Schedule Of Equity Method Investments [Line Items]
Number of properties contributed to a joint venture | property	8
Area of Real Estate Property | ft²	1,293,197
Aggregate gross sales price of a joint venture	$ 312,000
Impairment on assets held for sale		56,900
Closing costs	2,200
Working capital contributions	600
Cash proceeds at settlement	262,400
Net gain on disposition of real estate	$ 400
Herndon Innovation Center Metro Portfolio Venture, LLC [Member] | Metropolitan Washington, D.C. - Office [Member]
Schedule Of Equity Method Investments [Line Items]
Number of properties contributed to a joint venture | property	8
Area of Real Estate Property | ft²	1,293,197
Aggregate gross sales price of a joint venture	$ 312,000
Equity method investment percentage	15.00%
Equity method investment percentage of parnter	85.00%
Impairment on assets held for sale		$ 56,900
Closing costs	$ 2,200
Working capital contributions	600
Net gain on disposition of real estate	400
Cash paid for acquisition	$ 265,200

Real Estate Investments - Sum_3

Real Estate Investments - Summary of Land Parcels Sold (Details) $ in Thousands		Mar. 16, 2018USD ($)aParcel	Jan. 10, 2018USD ($)aParcel	Apr. 28, 2017USD ($)aParcel	Jan. 30, 2017USD ($)aParcel	Dec. 31, 2018USD ($)aParcel	Dec. 31, 2017USD ($)aParcel		Dec. 31, 2016USD ($)aParcel
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Sales Price						$ 359,300
Proceeds from the sale of properties						324,090	$ 171,860		$ 784,331
Gain on Sale						$ 3,040	$ 953		$ 9,232
Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel						2	5		3
Acreage of land | a						19.7	76.4		122.9
Sales Price						$ 15,056	$ 29,600		$ 14,938
Proceeds from the sale of properties						14,921	28,618		14,532
Gain on Sale						$ 1,537	$ 953		$ 9,232	[1]
Land [Member] | Garza Ranch - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel		1
Acreage of land | a		6.6
Sales Price		$ 14,571
Proceeds from the sale of properties		14,509
Gain on Sale		$ 1,515
Land [Member] | Westpark Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel			1
Acreage of land | a			13.1
Sales Price			$ 485
Proceeds from the sale of properties			412
Gain on Sale			$ 22
Land [Member] | 50 E. Swedesford Square [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel							1
Acreage of land | a							12
Sales Price							$ 7,200
Proceeds from the sale of properties							7,098
Gain on Sale							$ 882
Land [Member] | Bishops Gate [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel							1
Acreage of land | a							49.5
Sales Price							$ 6,000
Proceeds from the sale of properties							5,640
Gain on Sale	[2]						$ 71
Land [Member] | Garza Ranch - Multi-family [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel				1			1
Acreage of land | a				8.4			8.4
Sales Price				$ 11,800			$ 11,800
Proceeds from the sale of properties				11,560			11,560
Gain on Sale				$ 1,311			$ 0	[3]
Land [Member] | Gateway Land - Site C [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel							1
Acreage of land | a							4.8
Sales Price							$ 1,100
Proceeds from the sale of properties							1,043
Gain on Sale	[4]						$ 0
Land [Member] | Garza Ranch - Hotel [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel					1		1
Acreage of land | a					1.7		1.7
Sales Price					$ 3,500		$ 3,500
Proceeds from the sale of properties					3,277		3,277
Gain on Sale					$ 192		$ 0
Land [Member] | Oakland Lot B [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel									1
Acreage of land | a									0.9
Sales Price									$ 13,750
Proceeds from the sale of properties									13,411
Gain on Sale	[1]								$ 9,039
Land [Member] | Highlands Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel									1
Acreage of land | a									2
Sales Price									$ 288
Proceeds from the sale of properties									284
Gain on Sale	[1]								$ 193
Land [Member] | Greenhills Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel									1
Acreage of land | a									120
Sales Price									$ 900
Proceeds from the sale of properties									837
Gain on Sale	[1],[5]								$ 0
[1]	Gain on Sale is net of closing and other transaction related costs.
[2]	During the fourth quarter of 2016, the Company recognized an impairment of $3.0 million. During the second quarter of 2017, the Company recorded a held for sale impairment charge of $0.3 million, reducing the aggregate carrying value of the land parcel from $5.9 million to its estimated fair value less costs to sell of $5.6 million. The fair value measurement is based on pricing in the purchase and sale agreement for the property. As the pricing in the purchase and sale agreement is unobservable, the Company determined that the input utilized to determine fair value for the property falls within Level 3 in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The land parcel was sold on July 18, 2017.
[3]	The Company has a continuing involvement in this property through a completion guaranty, which requires the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. The Company recorded the cash received at settlement as “Deferred income, gains and rent” on the Company’s consolidated balance sheet and the Company will recognize the sale upon completion of infrastructure improvements.
[4]	During the fourth quarter of 2016, the Company recognized a nominal impairment related to this land parcel.
[5]	The carrying value of the land exceeded the fair value less the anticipated costs of sale as of December 31, 2015. Therefore the Company recognized an impairment loss of $0.3 million during the three-month period ended December 31, 2015. There was no gain or loss recognized on the sale during 2016

Real Estate Investments - Sum_4

Real Estate Investments - Summary of Land Parcels Sold (Parenthetical) (Details)	3 Months Ended			12 Months Ended
	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2018USD ($)Parcel	Dec. 31, 2017USD ($)Parcel	Dec. 31, 2016USD ($)	Jun. 30, 2018USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain/(Loss) on Sale				$ 2,932,000	$ 31,657,000	$ 116,983,000
Garza Ranch - Office [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel				3	2
Aggregate deferred gain recognized				$ 200,000			$ 2,800,000
Bishops Gate [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Provision for impairment on assets held for sale	$ 300,000	$ 3,000,000
Carrying value of real estate prior to impairment	5,900,000
Aggregate carrying value	$ 5,600,000
Greenhills Land [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Provision for impairment on assets held for sale			$ 300,000
Gain/(Loss) on Sale						$ 0

Real Estate Investments - Dispo

Real Estate Investments - Dispositions (Textual) (Details)	Mar. 31, 2017USD ($)property	Sep. 30, 2018USD ($)ft²	Dec. 31, 2017USD ($)aParcel	Mar. 31, 2017USD ($)property	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)property	Jun. 30, 2017USD ($)	Sep. 30, 2018USD ($)ft²property	Dec. 31, 2018USD ($)ft²apropertyParcel	Dec. 31, 2017USD ($)aParcel	Dec. 31, 2016USD ($)	Dec. 31, 2016	Dec. 31, 2016property	Dec. 31, 2016a	Dec. 31, 2016Parcel	Dec. 31, 2016Office
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties | property									97
Aggregate carrying values of properties			$ 3,832,348,000						$ 3,953,319,000	$ 3,832,348,000
Number of Properties Sold | property									10
Rentable Square Feet | ft²									1,414,457
Assets held for sale, net			$ 392,000						$ 11,599,000	392,000
Net gain on disposition of real estate									2,932,000	31,657,000	$ 116,983,000
Impairment charges					$ 1,800,000				$ 71,707,000	$ 3,057,000	40,517,000
Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Acreage of land | a			76.4						19.7	76.4				122.9
Number of Parcels | Parcel			5						2	5					3
Metropolitan Washington, D.C. - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Provision for impairment on assets held for sale		$ 56,900,000
2970 Market Street (Cira Square) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net gain on disposition of real estate				$ 500,000
Assets Held-for-sale [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets held for sale, net									$ 11,599,000		41,718,000
Impairment charges									$ 0
Acreage of land | a			13.1							13.1
Assets Held-for-sale [Member] | Land Held For Development [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets held for sale, net			$ 400,000							$ 400,000
Assets Held-for-sale [Member] | Metropolitan Washington, D.C. - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment Hold Period								10 years
Number of Properties Sold | property								8
Rentable Square Feet | ft²		1,293,197						1,293,197
Assets held for sale, net											9,785,000
Provision for impairment on assets held for sale								$ 56,900,000
Assets Held-for-sale [Member] | Metropolitan Washington, D.C. - Office [Member] | Office Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets held for sale, net		$ 366,000,000						366,000,000
Assets held for sale, fair value		$ 309,100,000						$ 309,100,000
Residual Capitalization Rates [Member] | Assets Held-for-sale [Member] | Metropolitan Washington, D.C. - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale		0.0747						0.0747
Discount Rates [Member] | Assets Held-for-sale [Member] | Metropolitan Washington, D.C. - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale		0.0860						0.0860
Other [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties	4			4					1				3			2
Impairment of properties held for use	$ 1,000,000								$ 14,800,000		7,300,000
Carrying value of real estate prior to impairment			10,200,000						$ 52,800,000	10,200,000	$ 25,800,000
Impairment Hold Period	10 years								10 years		10 years
Impairment charges			0
Aggregate carrying value											$ 18,500,000
Other [Member] | Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment of properties held for use											5,600,000
Carrying value of real estate prior to impairment											18,200,000
Impairment charges			0				$ 300,000
Acreage of land | a														108
Aggregate carrying value											$ 12,600,000
Number of Parcels | Parcel															5
Other [Member] | Impairment on Held for Use Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Aggregate carrying values of properties			$ 9,200,000						$ 38,000,000	$ 9,200,000
Other [Member] | Residual Capitalization Rates [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale	0.0900			0.0900					0.075			0.0875
Other [Member] | Discount Rates [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale	0.0925			0.0925					0.095			0.0900
Metropolitan DC [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties						2										3
Impairment of properties held for use					3,900,000	$ 7,400,000
Carrying value of real estate prior to impairment					$ 37,400,000	$ 51,900,000
Impairment Hold Period					10 years	10 years
Aggregate carrying value					$ 33,500,000	$ 44,500,000
Metropolitan DC [Member] | Residual Capitalization Rates [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale					0.0775	0.070
Metropolitan DC [Member] | Discount Rates [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale					0.0825	0.070

Real Estate Investments - Sum_5

Real Estate Investments - Summary of Properties Classified as Held for Sale Included in Continuing Operations (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
ASSETS HELD FOR SALE
Total assets held for sale, net	$ 11,599	$ 392
Held for Sale Properties Included in Continuing Operations [Member]
ASSETS HELD FOR SALE
Land inventory	11,599
Total real estate investments	11,599		$ 41,718
Total assets held for sale, net	11,599		41,718
Operating properties			73,591
Accumulated depreciation			(32,916)
Operating real estate investments, net			40,675
Land held for development			1,043
LIABILITIES HELD FOR SALE
Other liabilities			81
Total liabilities held for sale			81
Held for Sale Properties Included in Continuing Operations [Member] | Pennsylvania Suburbs - Land [Member]
ASSETS HELD FOR SALE
Land inventory	4,254
Total real estate investments	4,254
Total assets held for sale, net	4,254
Held for Sale Properties Included in Continuing Operations [Member] | Metropolitan Washington, D.C. - Office [Member]
ASSETS HELD FOR SALE
Total real estate investments			9,785
Total assets held for sale, net			9,785
Operating properties			21,720
Accumulated depreciation			(11,935)
Operating real estate investments, net			9,785
Land held for development			0
LIABILITIES HELD FOR SALE
Other liabilities			73
Total liabilities held for sale			73
Held for Sale Properties Included in Continuing Operations [Member] | Other Segment - Office [Member]
ASSETS HELD FOR SALE
Total real estate investments			30,890
Total assets held for sale, net			30,890
Operating properties			51,871
Accumulated depreciation			(20,981)
Operating real estate investments, net			30,890
Land held for development			0
LIABILITIES HELD FOR SALE
Other liabilities			8
Total liabilities held for sale			8
Held for Sale Properties Included in Continuing Operations [Member] | Other Segment - Land [Member]
ASSETS HELD FOR SALE
Land inventory	7,345
Total real estate investments	7,345		1,043
Total assets held for sale, net	$ 7,345		1,043
Operating properties			0
Accumulated depreciation			0
Operating real estate investments, net			0
Land held for development			1,043
LIABILITIES HELD FOR SALE
Other liabilities			0
Total liabilities held for sale			$ 0

Real Estate Investments - Sum_6

Real Estate Investments - Summary of Properties Classified as Held for Sale Included in Continuing Operations (Parenthetical) (Details)	3 Months Ended		12 Months Ended
	Dec. 31, 2016USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2018USD ($)propertyParcel	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)property
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Provision for impairment		$ 1,800,000	$ 71,707,000	$ 3,057,000	$ 40,517,000
Number of Properties Sold | property			10
Held for Sale Properties Included in Continuing Operations [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Provision for impairment			$ 0
Held for Sale Properties Included in Continuing Operations [Member] | Metropolitan Washington, D.C. - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property					3
Provision for impairment on assets held for sale	$ 3,000,000
Impairment Hold Period					10 years
Held for Sale Properties Included in Continuing Operations [Member] | Other Segment - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property					2
Provision for impairment on assets held for sale	$ 11,500,000
Impairment Hold Period					10 years
Held for Sale Properties Included in Continuing Operations [Member] | Residual Capitalization Rates [Member] | Metropolitan Washington, D.C. - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale	0.0900				0.0900
Held for Sale Properties Included in Continuing Operations [Member] | Residual Capitalization Rates [Member] | Other Segment - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale	0.0975				0.0975
Held for Sale Properties Included in Continuing Operations [Member] | Discount Rates [Member] | Metropolitan Washington, D.C. - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale	0.1000				0.1000
Held for Sale Properties Included in Continuing Operations [Member] | Discount Rates [Member] | Other Segment - Office [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale	0.0975				0.0975
Held for Sale Properties Included in Continuing Operations [Member] | Pennsylvania Suburbs - Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel			1
Held for Sale Properties Included in Continuing Operations [Member] | Other - Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel			2

Real Estate Investments - Sum_7

Real Estate Investments - Summary of Office Properties Sold (Details) $ in Thousands		Mar. 15, 2017USD ($)ft²	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)ft²property	Dec. 31, 2017USD ($)ft²property	Dec. 31, 2016USD ($)ft²property
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property				10
Rentable Square Feet | ft²				1,414,457
Sales Price				$ 359,300
Proceeds from the sale of properties				324,090	$ 171,860	$ 784,331
Gain/(Loss) on Sale				$ 2,932	$ 31,657	$ 116,983
Philadelphia Marine Center (Marine Piers) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Rentable Square Feet | ft²		181,900			181,900
Sales Price		$ 21,400			$ 21,400
Proceeds from the sale of properties		11,200			11,200
Gain/(Loss) on Sale		$ 6,500			$ 6,500
2970 Market Street (Cira Square) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain/(Loss) on Sale			$ 500
Office Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property						66
Rentable Square Feet | ft²						5,239,632
Sales Price						$ 820,000
Proceeds from the sale of properties						769,799
Gain/(Loss) on Sale	[1]					$ 116,983
Office Properties [Member] | 11, 14, 15, 17 and 18 Campus Boulevard (Newtown Square) [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					252,802
Sales Price					$ 42,000
Proceeds from the sale of properties					40,459
Gain/(Loss) on Sale	[1]				$ 19,642
Office Properties [Member] | 630 Allendale Road [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property					1
Rentable Square Feet | ft²					150,000
Sales Price					$ 17,500
Proceeds from the sale of properties					16,580
Gain/(Loss) on Sale	[1]				$ 3,605
Office Properties [Member] | Two, Four A, Four B and Five Eves Drive (Evesham Corporate Center) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property					4
Rentable Square Feet | ft²					134,794
Sales Price					$ 9,700
Proceeds from the sale of properties					8,650
Gain/(Loss) on Sale	[1],[2]				$ (325)
Office Properties [Member] | 200, 210 & 220 Lake Drive East (Woodland Falls) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property					3
Rentable Square Feet | ft²					215,465
Sales Price					$ 19,000
Proceeds from the sale of properties					17,771
Gain/(Loss) on Sale	[1],[3]				$ (249)
Office Properties [Member] | 11700, 11710, 11720 & 11740 Beltsville Drive (Calverton) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property					3
Rentable Square Feet | ft²					313,810
Sales Price					$ 9,000
Proceeds from the sale of properties					8,354
Gain/(Loss) on Sale	[1],[4]				$ 0
Office Properties [Member] | 1200 & 1220 Concord Avenue (Concord Airport Plaza) [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					350,256
Sales Price					$ 33,100
Proceeds from the sale of properties					32,010
Gain/(Loss) on Sale	[1]				$ 551
Office Properties [Member] | 620, 640, 660 Allendale Road [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property						3
Rentable Square Feet | ft²						156,669
Sales Price						$ 12,800
Proceeds from the sale of properties						12,014
Gain/(Loss) on Sale	[1]					$ 2,382
Office Properties [Member] | 1120 Executive Plaza [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property						1
Rentable Square Feet | ft²						95,183
Sales Price						$ 9,500
Proceeds from the sale of properties						9,241
Gain/(Loss) on Sale	[1],[5]					$ (18)
Office Properties [Member] | 50 East Clementon Road [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property						1
Rentable Square Feet | ft²						3,080
Sales Price						$ 1,100
Proceeds from the sale of properties						1,011
Gain/(Loss) on Sale	[1]					$ (85)
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]
Number of Properties Sold | property						2
Rentable Square Feet | ft²						197,225
Sales Price						$ 44,500
Proceeds from the sale of properties						43,412
Gain/(Loss) on Sale	[1],[6]					$ (752)
Office Properties [Member] | 2970 Market Street (Cira Square) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property						1
Rentable Square Feet | ft²						862,692
Sales Price						$ 354,000
Proceeds from the sale of properties						350,150
Gain/(Loss) on Sale	[1]					$ 115,828
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
Rentable Square Feet | ft²						3,924,783
Sales Price						$ 398,100
Proceeds from the sale of properties						353,971
Gain/(Loss) on Sale	[1],[7]					$ (372)
Retail Properties [Member] | 7000 Midlantic Drive [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property					1
Rentable Square Feet | ft²					10,784
Sales Price					$ 8,200
Proceeds from the sale of properties					7,714
Gain/(Loss) on Sale	[1]				$ 1,413
Mixed-use Properties [Member] | Philadelphia Marine Center (Marine Piers) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property					1
Rentable Square Feet | ft²					181,900
Sales Price					$ 21,400
Proceeds from the sale of properties					11,182
Gain/(Loss) on Sale	[1],[8]				$ 6,498
Office, Retail and Mixed-use Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties Sold | property					20
Rentable Square Feet | ft²					1,609,811
Sales Price					$ 159,900
Proceeds from the sale of properties					142,720
Gain/(Loss) on Sale	[1]				$ 31,135
[1]	Gain/(Loss) on Sale is net of closing and other transaction related costs.
[2]	As of March 31, 2017, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of four properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $1.0 million at March 31, 2017, which reduced the aggregate carrying values of the properties from $10.2 million to their estimated fair value of $9.2 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.00% and 9.25%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs.
[3]	As of December 31, 2016, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of three properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $7.3 million at December 31, 2016, reducing the aggregate carrying values of the properties from $25.8 million to their estimated fair value of $18.5 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 8.75% and 9.00%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs
[4]	During the fourth quarter of 2016, the Company recognized a $3.0 million impairment related to these properties. During the first quarter of 2017, there was a price reduction of $1.7 million under the agreement of sale and an additional impairment of $1.7 million was recognized
[5]	As of June 30, 2016, the Company determined that the sale of the property was probable and classified this property as held for sale in accordance with applicable accounting standards for long lived assets. At such date, the carrying value of the property exceeded the fair value less the anticipated costs of sale. As a result, the Company recognized a provision for impairment totaling approximately $1.8 million during the three-month period ended June 30, 2016. The fair value measurement was based on the pricing in the purchase and sale agreement for the sale of the property. As the pricing in the purchase and sale agreement is unobservable, the Company determined that the inputs utilized to determine fair value for this property falls within Level 3 in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, "Fair Value Measurements and Disclosures.” The loss on sale represents additional closing costs recognized at closing.
[6]	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
[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 March 15, 2017, the Company sold its sublease interest in the Piers at Penn’s Landing (the “Marine Piers”), which includes leasehold improvements containing 181,900 net rentable square feet, and a marina, located in Philadelphia, Pennsylvania for an aggregate sales price of $21.4 million. On the closing date, the buyer paid $12.0 million in cash. The $9.4 million balance of the purchase is due on (a) January 31, 2020, in the event that the tenant at the Marine Piers does not exercise an option it holds to extend the term of the sublease or (b) January 15, 2024, in the event that the tenant does exercise the option to extend the term of the sublease. The Company determined that it is appropriate to account for the sales transaction under the cost recovery method. The Company received cash proceeds of $11.2 million, after closing costs and prorations, and the net book value of the Marine Piers was $4.7 million, resulting in a gain on sale of $6.5 million. The remaining gain on sale of $9.4 million will be recognized on the second purchase price installment date. Prior to its sale, the Marine Piers had been classified as mixed-use within the Company’s property count

Real Estate Investments - Sum_8

Real Estate Investments - Summary of Office Properties Sold (Parenthetical) (Details)		Mar. 31, 2017USD ($)property	Mar. 15, 2017USD ($)ft²	Dec. 31, 2017USD ($)ft²	Mar. 31, 2017USD ($)property	Dec. 31, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2018USD ($)ft²property	Dec. 31, 2017USD ($)ft²	Dec. 31, 2016USD ($)	Dec. 31, 2016	Dec. 31, 2016property	Dec. 31, 2016ft²	Dec. 31, 2016Office
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties | property										97
Aggregate carrying values of properties				$ 3,832,348,000						$ 3,953,319,000	$ 3,832,348,000
Provision for impairment							$ 1,800,000			$ 71,707,000	3,057,000	$ 40,517,000
Rentable Square Feet | ft²										1,414,457
Sales Price										$ 359,300,000
Proceeds from the sale of properties										324,090,000	171,860,000	784,331,000
Assets held for sale, net				$ 392,000						11,599,000	392,000
Gain/(Loss) on Sale										$ 2,932,000	$ 31,657,000	116,983,000
Office Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties | property										88
Rentable Square Feet | ft²															5,239,632
Sales Price						$ 820,000,000						820,000,000
Proceeds from the sale of properties												769,799,000
Gain/(Loss) on Sale	[1]											116,983,000
200, 210 & 220 Lake Drive East (Woodland Falls) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Carrying value of real estate prior to impairment						$ 25,800,000						25,800,000
Impairment Hold Period						10 years
Provision for impairment						$ 7,300,000
Aggregate carrying value						18,500,000						18,500,000
200, 210 & 220 Lake Drive East (Woodland Falls) [Member] | Office Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Rentable Square Feet | ft²				215,465							215,465
Sales Price				$ 19,000,000							$ 19,000,000
Proceeds from the sale of properties											17,771,000
Gain/(Loss) on Sale	[1],[2]										$ (249,000)
Philadelphia Marine Center (Marine Piers) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Rentable Square Feet | ft²			181,900	181,900							181,900
Sales Price			$ 21,400,000	$ 21,400,000							$ 21,400,000
Payment by cash on purchases			12,000,000								12,000,000
Balance payment on purchases			$ 9,400,000	9,400,000							$ 9,400,000
Date of second installment payment			Jan. 31, 2020								Jan. 31, 2020
Proceeds from the sale of properties			$ 11,200,000								$ 11,200,000
Assets held for sale, net			4,700,000	4,700,000							4,700,000
Gain/(Loss) on Sale			6,500,000								6,500,000
Deferred gain on sale			$ 9,400,000	$ 9,400,000							$ 9,400,000
11700, 11710, 11720 & 11740 Beltsville Drive (Calverton) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Provision for impairment on assets held for sale					$ 1,700,000	3,000,000
Purchase price reduction					$ 1,700,000
11700, 11710, 11720 & 11740 Beltsville Drive (Calverton) [Member] | Office Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Rentable Square Feet | ft²				313,810							313,810
Sales Price				$ 9,000,000							$ 9,000,000
Proceeds from the sale of properties											8,354,000
Gain/(Loss) on Sale	[1],[3]										0
1200 & 1220 Concord Avenue (Concord Airport Plaza) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Provision for impairment on assets held for sale											$ 32,000
Proceeds after closing costs and prorations						11,500
1200 & 1220 Concord Avenue (Concord Airport Plaza) [Member] | Office Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Rentable Square Feet | ft²				350,256							350,256
Sales Price				$ 33,100,000							$ 33,100,000
Proceeds from the sale of properties											32,010,000
Gain/(Loss) on Sale	[1]										551,000
196/198 Van Buren Street (Herndon Metro Plaza I&II) [Member] | Office Properties [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
Rentable Square Feet | ft²															197,225
Sales Price						44,500,000						44,500,000
Proceeds from the sale of properties												43,412,000
Gain/(Loss) on Sale	[1],[4]											(752,000)
Och Ziff Portfolio [Member] | Office Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Rentable Square Feet | ft²															3,924,783
Sales Price						398,100,000						398,100,000
Proceeds from the sale of properties												353,971,000
Gain/(Loss) on Sale	[1],[5]											(372,000)
Provision for impairment on assets held for sale									$ 45,400,000
Residual Capitalization Rates [Member] | 200, 210 & 220 Lake Drive East (Woodland Falls) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale													0.0875
Discount Rates [Member] | 200, 210 & 220 Lake Drive East (Woodland Falls) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale													0.0900
Other [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties		4			4					1				3		2
Impairment of properties held for use		$ 1,000,000								$ 14,800,000		7,300,000
Carrying value of real estate prior to impairment				10,200,000		25,800,000				$ 52,800,000	10,200,000	$ 25,800,000
Impairment Hold Period		10 years								10 years		10 years
Provision for impairment				0
Aggregate carrying value						$ 18,500,000						$ 18,500,000
Other [Member] | 200, 210 & 220 Lake Drive East (Woodland Falls) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Properties | property														3
Other [Member] | Impairment on Held for Use Properties [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Aggregate carrying values of properties				$ 9,200,000						$ 38,000,000	$ 9,200,000
Other [Member] | Residual Capitalization Rates [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale		0.0900			0.0900					0.075			0.0875
Other [Member] | Discount Rates [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale		0.0925			0.0925					0.095			0.0900
[1]	Gain/(Loss) on Sale is net of closing and other transaction related costs.
[2]	As of December 31, 2016, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of three properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $7.3 million at December 31, 2016, reducing the aggregate carrying values of the properties from $25.8 million to their estimated fair value of $18.5 million. The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 8.75% and 9.00%, respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy established by Accounting Standards Codification (ASC) Topic 820, “Fair Value Measurements and Disclosures.” The loss on sale in the table above represents additional closing costs
[3]	During the fourth quarter of 2016, the Company recognized a $3.0 million impairment related to these properties. During the first quarter of 2017, there was a price reduction of $1.7 million under the agreement of sale and an additional impairment of $1.7 million was recognized
[4]	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
[5]	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

Investment in Unconsolidated _3

Investment in Unconsolidated Real Estate Ventures (Textual) (Details)		Dec. 28, 2018USD ($)ft²property	Dec. 20, 2018USD ($)ft²property	Dec. 11, 2018USD ($)ft²property	Aug. 01, 2018USD ($)	Jun. 26, 2018USD ($)	Jan. 10, 2018USD ($)property	Jan. 05, 2018USD ($)ft²	Oct. 18, 2017USD ($)ft²property	Oct. 17, 2017USD ($)property	Sep. 14, 2017USD ($)ft²property	Jan. 31, 2017USD ($)property	Jun. 10, 2016USD ($)	Mar. 02, 2016USD ($)	Feb. 04, 2016USD ($)ft²property	May 29, 2015USD ($)a	Jan. 30, 2015USD ($)	Oct. 27, 2014ft²Apartment_unitStoreyNumberofCar.	Oct. 21, 2014USD ($)	Oct. 17, 2014USD ($)ft²property	Jul. 31, 2014USD ($)ft²propertyStorey	Oct. 16, 2013USD ($)ft²property	Jul. 31, 2013USD ($)ft²aproperty	Dec. 31, 2018USD ($)ft²apropertyReal_Estate_InvestmentApartment_unit		Sep. 30, 2018USD ($)property	Sep. 30, 2017USD ($)property	Sep. 30, 2016USD ($)	Dec. 31, 2018USD ($)ft²apropertyReal_Estate_InvestmentApartment_unit		Dec. 31, 2017USD ($)		Dec. 31, 2016USD ($)ft²property	Dec. 31, 2011USD ($)	Dec. 31, 2015ft²propertyStorey	Dec. 31, 2014USD ($)	Oct. 15, 2014	Apr. 03, 2014ft²propertyStorey	Dec. 31, 2013USD ($)	Jan. 25, 2013USD ($)aStoreyBed	Jul. 10, 2012USD ($)ft²property	Jan. 20, 2011a
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method																								$ 169,100,000					$ 169,100,000		$ 194,621,000		$ 281,331,000
Rentable Square Feet | ft²																								1,414,457					1,414,457
Accounts receivable																								$ 16,394,000					$ 16,394,000		17,938,000
Area of Real Estate Property | ft²																								16,777,249					16,777,249
Gross sales price																								$ 359,300,000					$ 359,300,000
Proceeds from the sale of properties																													324,090,000		171,860,000		784,331,000
Net gain on disposition of real estate																													$ 2,932,000		31,657,000		116,983,000
Number of Properties | property																								97					97
Acquisition of properties																													$ 196,625,000		72,523,000		20,406,000
Proceeds from repayment of mortgage notes receivable																													$ 192,000		151,000		0
Number of Properties Sold | property																													10
Real estate ventures aggregate indebtedness to third parties																								$ 370,319,000					$ 370,319,000		768,912,000
Net gain on real estate venture transactions																													142,233,000		80,526,000		20,000,000
Property encumbered at the time of venture sale																								$ 323,032,000					323,032,000
Proceeds from real estate venture sales																													$ 60,346,000		145,416,000		21,022,000
Number of office properties owned | property																								2					2
Assets held for sale, net																								$ 11,599,000					$ 11,599,000		392,000
Debt, net																								365,707,000					365,707,000		766,420,000
Advance received for refinancing																													455,500,000		341,000,000		195,000,000
Cash distribution from unconsolidated real estate ventures																													6,526,000		20,781,000		13,065,000
Advanced under the construction loan																													908,000		6,638,000		$ 28,610,000
Secured Debt [Member]
Schedule Of Equity Method Investments [Line Items]
Real estate property debt																								323,032,000					323,032,000		$ 320,107,000
Fairview Properties [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method																								11,700,000					11,700,000
Equity method investment other than temporary impairment charge																													4,100,000
Encino Trace - Land [Member]
Schedule Of Equity Method Investments [Line Items]
Rentable Square Feet | ft²																																			320,000
Number of Properties | property																																			2
Number of floors of a building | Storey																																			4
DRA Austin Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage				50.00%
Service and other revenue																													$ 3,400,000
Area of Real Estate Property | ft²				1,570,123
Number of Properties | property				12
Net gain on real estate venture transactions				$ 103,800,000																				$ 103,800,000
Percentage of ownership interests				50.00%
Aggregate purchase price				$ 535,100,000
Unaffiliated Third Party [Member]
Schedule Of Equity Method Investments [Line Items]
Percentage of ownership interests																																					50.00%
Brandywine Realty Trust [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage																															50.00%
Equity Method Investment, Additional Distribution Rights																															10.00%
DRA Advisors LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage																															50.00%
Metropolitan Washington, D.C. - Office [Member]
Schedule Of Equity Method Investments [Line Items]
Number of properties contributed to a joint venture | property																										8
Impairment on assets held for sale																										$ 56,900,000
Four Points Centre [Member]
Schedule Of Equity Method Investments [Line Items]
Number of Properties | property																																						2
Number of floors of a building | Storey																																						3
Evo at Cira Disposition [Member]
Schedule Of Equity Method Investments [Line Items]
Gross sales price							$ 197,500,000
Net gain on real estate venture transactions							25,700,000
Cost of equity method investment							17,300,000
Proceeds from real estate venture sales							$ 43,000,000
Sale of ownership interest percentage							50.00%
Number of property units sold | property							345
Evo at Cira Disposition [Member] | Philadelphia [Member] | Pennsylvania [Member]
Schedule Of Equity Method Investments [Line Items]
Construction Loan							$ 110,900,000
TB-BDN Plymouth Apartments [Member]
Schedule Of Equity Method Investments [Line Items]
Gross sales price												$ 100,500,000
Number of Properties Sold | property												398
Net gain on real estate venture transactions												$ 14,600,000
Percentage of ownership interests												50.00%
Proceeds from real estate venture sales												$ 27,200,000
Sale of ownership interest percentage												50.00%
Allocated gross sales value of ownership interest, percentage												50.00%
Guarantee obligations cancelled												$ 3,200,000
TB-BDN Plymouth Apartments [Member] | Pennsylvania [Member]
Schedule Of Equity Method Investments [Line Items]
Construction Loan												54,000,000
Office Properties [Member]
Schedule Of Equity Method Investments [Line Items]
Rentable Square Feet | ft²																																	5,239,632
Area of Real Estate Property | ft²																								15,609,156					15,609,156
Gross sales price																																	$ 820,000,000
Proceeds from the sale of properties																																	769,799,000
Net gain on disposition of real estate	[1]																																$ 116,983,000
Number of Properties | property																								88					88
Number of Properties Sold | property																																	66
Real Estate Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Accounts receivable																								$ 800,000					$ 800,000		$ 900,000
Real Estate Venture [Member] | Management Fees [Member]
Schedule Of Equity Method Investments [Line Items]
Service and other revenue																													6,300,000		6,400,000		$ 6,700,000
Real Estate Venture [Member] | Leasing Commission Income [Member]
Schedule Of Equity Method Investments [Line Items]
Service and other revenue																													$ 2,500,000		4,500,000		$ 3,800,000
Unconsolidated Real Estate Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Number of unconsolidated investments in Real Estate Ventures | Real_Estate_Investment																								10					10
Investment in Real Estate Ventures, equity method																								$ 169,100,000					$ 169,100,000
Real estate ventures aggregate indebtedness to third parties																								370,319,000					370,319,000
Equity method investment other than temporary impairment charge	[2]																												4,076,000		4,844,000
Debt, net																								$ 365,707,000					$ 365,707,000
Unconsolidated Real Estate Ventures [Member] | TB-BDN Plymouth Apartments [Member]
Schedule Of Equity Method Investments [Line Items]
Equity in income (loss) of Real Estate Ventures												$ 12,600,000
Unconsolidated Real Estate Ventures [Member] | Minimum [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage																								15.00%					15.00%
Unconsolidated Real Estate Ventures [Member] | Maximum [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage																								70.00%					70.00%
Unconsolidated Real Estate Ventures [Member] | Six 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																								6					6
Rentable Square Feet | ft²																								5,800,000					5,800,000
Unconsolidated Real Estate Ventures [Member] | Two Real Estate Ventures [Member] | Land Held For Development [Member]
Schedule Of Equity Method Investments [Line Items]
Number of unconsolidated investments in Real Estate Ventures | Real_Estate_Investment																								2					2
Acreage of land | a																								1.4					1.4
Unconsolidated Real Estate Ventures [Member] | One Real Estate Venture [Member] | Land Under Active Development [Member]
Schedule Of Equity Method Investments [Line Items]
Number of unconsolidated investments in Real Estate Ventures | Real_Estate_Investment																								1					1
Acreage of land | a																								1.3					1.3
Unconsolidated Real Estate Ventures [Member] | Two Other Real Estate Ventures [Member] | Residential Tower [Member]
Schedule Of Equity Method Investments [Line Items]
Number of unconsolidated investments in Real Estate Ventures | Real_Estate_Investment																								1					1
Number of Property units | Apartment_unit																								321					321
Herndon Innovation Center Metro Portfolio Venture, LLC [Member] | Metropolitan Washington, D.C. - Office [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage			15.00%
Number of properties contributed to a joint venture | property			8
Area of Real Estate Property | ft²			1,293,197
Gross sales price			$ 312,000,000
Cash proceeds received from sale of properties			265,200,000
Closing costs			2,200,000
Working capital contribution			600,000
Proceeds from the sale of properties			262,400,000
Net gain on disposition of real estate			400,000
Capital credit			47,700
Impairment on assets held for sale																										$ 56,900,000
Aggregate gross sales price of a joint venture			$ 312,000,000
Herndon Innovation Center Metro Portfolio Venture, LLC [Member] | Metropolitan Washington, D.C. - Office [Member] | Rockpoint [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage			85.00%
Austin Joint Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Rentable Square Feet | ft²									1,164,496											590,881	232,274
Equity method investment percentage									50.00%
Gross sales price									$ 333,250,000
Closing costs																				$ 200,000	$ 100,000
Number of Properties | property																				7	2
Equity method investment, Consideration transferred																					$ 48,200,000
Mortgage loans outstanding																					$ 34,500,000
Mortgage loans interest rate																					3.87%
Equity method investments, Cash contributions																				$ 18,900,000	$ 12,800,000
Equity Method Investments Purchase Adjustments																					900,000
Business acquisition cost of acquired entity transaction costs borne by seller																					600,000
Acquisition of properties																				128,100,000
Short-term Bank Loans and Notes Payable																				$ 88,000,000
Number of Properties Sold | property									8	7
Real estate ventures aggregate indebtedness to third parties									$ 150,968,000	$ 151,000,000
Cash proceeds after the payment of mortgage debt, closing costs and prorations									86,400,000
Net gain on real estate venture transactions									40,092,000
Deferred gain on sale									12,072,000
Proceeds from real estate venture sales									$ 172,742,000
Austin Joint Venture [Member] | Brandywine Realty Trust [Member]
Schedule Of Equity Method Investments [Line Items]
Number of properties contributed to a joint venture | property																						7
Area of Real Estate Property | ft²																						1,398,826
Aggregate gross sales price of a joint venture																						$ 330,000,000
Equity method investment, agreement to pay future capital expenditures																						5,200,000																	$ 800,000
Equity method investments, Cash contributions																					$ 6,400,000
Austin Joint Venture [Member] | DRA Advisors LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Closing costs																						1,900,000
Equity Method Investment, Distribution, Net of Initial Funding Agreement																						266,300,000
Amount Of Participant Contribution																						49,700,000
Closing Prorations and Lender Holdbacks																						6,900,000
Proceeds from Equity Method Investment, Dividends or Distributions																						271,500,000
Non-Recourse Debt																						$ 230,600,000
Austin Joint Venture [Member] | Office Properties [Member] | Four Points Centre [Member]
Schedule Of Equity Method Investments [Line Items]
Rentable Square Feet | ft²																																						192,396
Austin, Texas [Member]
Schedule Of Equity Method Investments [Line Items]
Number of floors of a building | Storey																					3
Austin, Texas [Member] | Brandywine Realty Trust [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment, agreement to pay future capital expenditures																																				$ 4,400,000
River Place [Member]
Schedule Of Equity Method Investments [Line Items]
Proceeds from repayment of mortgage notes receivable																	$ 88,000,000
Brandywine - AI Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	[3]																							$ 11,731,000					$ 11,731,000		$ 43,560,000
Rentable Square Feet | ft²		364,277									874,479
Equity method investment percentage																								50.00%	[3],[4]				50.00%	[3],[4]	50.00%		50.00%
Real estate ventures aggregate indebtedness to third parties	[3]																							$ 26,111,000					$ 26,111,000		$ 93,117,000
Impairment of properties held for use																													10,400,000
Equity method investment other than temporary impairment charge																											$ 4,800,000		$ 4,076,000	[2]	4,844,000	[2]
Number of office properties owned | property		2									5																5
Cost of equity method investment after recordation of impairment charge																											$ 44,300,000
Impairment Hold Period																											10 years		10 years
Effective interest rate	[3]																							4.65%					4.65%
Debt, net																								$ 26,020,000					$ 26,020,000		92,917,000
Brandywine - AI Venture [Member] | Residual Capitalization Rates [Member]
Schedule Of Equity Method Investments [Line Items]
Measurement input rate																								0.080			0.075		0.080
Brandywine - AI Venture [Member] | Station Square [Member]
Schedule Of Equity Method Investments [Line Items]
Rentable Square Feet | ft²																																									497,896
Equity method investment percentage																																									50.00%
Number of Properties | property																																									3
Impairment of properties held for use																												$ 10,400,000
Cost of equity method investment																																									$ 120,600,000
Equity method investment other than temporary impairment charge																												$ 5,200,000
Brandywine - AI Venture [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 [Member] | Station Square and 7101 Wisconsin Property Sale [Member]
Schedule Of Equity Method Investments [Line Items]
Rentable Square Feet | ft²		510,202									230,904
Equity method investment percentage		50.00%									50.00%
Gross sales price		$ 107,000,000									$ 105,700,000
Number of Properties Sold | property		3
Net gain on real estate venture transactions		$ 1,500,000									13,800,000
Property encumbered at the time of venture sale		66,500,000									37,400,000
Debt instrument prepayment penalty		700,000									800,000
Cash proceeds received from sale of venture		34,800,000									63,600,000
Proceeds from real estate venture sales		$ 17,400,000									$ 31,800,000
Brandywine - AI Venture [Member] | Fairview Properties [Member]
Schedule Of Equity Method Investments [Line Items]
Impairment of properties held for use																													20,800,000
Assets held for sale, net																								$ 50,400,000					50,400,000
Cost of equity method investment after recordation of impairment charge																								$ 15,800,000					$ 15,800,000
Brandywine - AI Venture [Member] | 3130 Fairview Park Drive [Member]
Schedule Of Equity Method Investments [Line Items]
Impairment Hold Period																													10 years
Brandywine - AI Venture [Member] | 3130 Fairview Park Drive [Member] | Residual Capitalization Rates [Member]
Schedule Of Equity Method Investments [Line Items]
Measurement input rate																								0.0800					0.0800
Brandywine - AI Venture [Member] | 3130 Fairview Park Drive [Member] | Discount Rates [Member]
Schedule Of Equity Method Investments [Line Items]
Measurement input rate																								0.0950					0.0950
Brandywine - AI Venture [Member] | 3141 Fairview Park Drive [Member] | Residual Capitalization Rates [Member]
Schedule Of Equity Method Investments [Line Items]
Measurement input rate																								0.0800					0.0800
Brandywine - AI Venture [Member] | 3141 Fairview Park Drive [Member] | Discount Rates [Member]
Schedule Of Equity Method Investments [Line Items]
Measurement input rate																								0.0800					0.0800
Brandywine - AI Venture [Member] | Minimum [Member] | Discount Rates [Member]
Schedule Of Equity Method Investments [Line Items]
Measurement input rate																								0.090			0.078		0.090
Brandywine - AI Venture [Member] | Maximum [Member] | Discount Rates [Member]
Schedule Of Equity Method Investments [Line Items]
Measurement input rate																								0.095			0.085		0.095
MAP Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	[5]																							$ 11,173,000					$ 11,173,000		15,450,000
Equity method investment percentage	[4],[5]																							50.00%					50.00%
Real estate ventures aggregate indebtedness to third parties	[5]																							$ 185,000,000					$ 185,000,000		180,800,000
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%
Gross sales price															$ 398,100,000
Proceeds from the sale of properties															354,000,000
Non-Recourse Debt															$ 180,800,000
Number of Properties Sold | property															58
Percentage of fee interests in land sold															100.00%
Ground lease extended expiration date																													2115-02
Ground lease annual payments																													$ 11,900,000
Ground lease annual rent expense increase percentage through November 2025																								2.50%					2.50%
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. Thereafter, annual rental payments increase by 2.5% or CPI at the discretion of the lessor.
Ground lease annual rent expense fixed increase percentage, end date																													2025-11
Ground lease annual rent expense increase after November 2025																								2.50%					2.50%
Ownership percentage value															$ 25,200,000
MAP Ground Lease Venture LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Real estate ventures aggregate indebtedness to third parties					$ 180,800,000
Debt Instrument Maturity Date					Feb. 9, 2019
MAP Ground Lease Venture LLC [Member] | Secured Debt [Member]
Schedule Of Equity Method Investments [Line Items]
Debt Instrument Maturity Date					Aug. 1, 2023
Indebtedness to third parties, refinanced amount					$ 185,000,000
Debt instrument, basis spread on variable rate					2.45%
MAP Ground Lease Venture LLC [Member] | Maximum [Member] | Secured Debt [Member]
Schedule Of Equity Method Investments [Line Items]
Effective interest rate					6.00%
1919 Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	[6]																							$ 19,897,000					$ 19,897,000		22,268,000
Equity method investment percentage						50.00%																		50.00%	[4],[6]				50.00%	[4],[6]												50.00%
Number of floors of a building | Storey																		29
Real estate ventures aggregate indebtedness to third parties	[6]																							$ 88,860,000					$ 88,860,000		88,860,000
Effective interest rate	[6]																							4.00%					4.00%
Payments to Acquire Land																																		$ 9,300,000
Area of developed parcels of land (in acres) owned by a Real Estate Venture | a																																										1
Remeasurement gain or loss on investments																																		$ 0
Square foot of contemporary glass tower development | ft²																		455,000
Number of luxury apartments | Apartment_unit																		321
Square feet of commercial space | ft²																		24,000
Number of Car Structured Parking Facility | NumberofCar.																		215
Development completion date																													Sep. 30, 2016
Debt, net						$ 44,400,000
Note receivable						$ 44,400,000
Loan interest rate						4.00%
Mortgage loans scheduled maturity date						Jun. 25, 2023
Repayment of construction loan						$ 88,800,000
Construction loan, principal amount						88,600,000
Accrued interest on construction loan						200,000
1919 Ventures [Member] | Other Assets [Member]
Schedule Of Equity Method Investments [Line Items]
Note receivable						44,400,000
1919 Ventures [Member] | Unaffiliated Third Party [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage																																										50.00%
1919 Ventures [Member] | LCOR/CalSTRS [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage																			50.00%
Aggregate gross sales price of a joint venture																			$ 16,400,000
Mortgage loans outstanding																															88,900,000
Equity method investments, Cash contributions																													$ 29,600,000
General Partners' Contributed Capital																			5,200,000
Net gain on sale of undepreciated real estate																			$ 8,200,000
Debt, net						$ 44,400,000
Four Tower Bridge [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	[7]																							$ 0					$ 0		3,032,000
Equity method investment percentage								35.00%																65.00%	[4],[7]				65.00%	[4],[7]
Real estate ventures aggregate indebtedness to third parties	[7]																							$ 0					$ 0		9,749,000
Net gain on real estate venture transactions								$ 11,600,000
Four Tower Bridge [Member] | Conshohocken [Member] | Pennsylvania [Member]
Schedule Of Equity Method Investments [Line Items]
Area of Real Estate Property | ft²								86,021
Real estate property debt								$ 9,700,000
Seven Tower Bridge [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	[7]																							$ 0					$ 0		471,000
Equity method investment percentage	[4],[7]																							20.00%					20.00%
Real estate ventures aggregate indebtedness to third parties	[7]																							$ 0					$ 0		$ 14,629,000
Sale of ownership interest percentage								20.00%
evo at Cira Centre South Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method														$ 28,300,000
Equity method investment percentage														50.00%										50.00%					50.00%		50.00%		50.00%							30.00%
Number of floors of a building | Storey																																								33
Cost of equity method investment																																								$ 4,000,000
Equity method investment other than temporary impairment charge	[2]																												$ 0		$ 0
Debt Instrument Maturity Date													Jul. 25, 2016
Area of developed parcels of land (in acres) owned by a Real Estate Venture | a																																								1
Debt, net																								$ 0	[8]				$ 0	[8]	110,136,000
Student housing bed capacity | Bed																																								850
Equity Method Investment, Underlying Equity in Net Assets																																							8,500,000	$ 8,500,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity																																							$ 4,500,000
Cash paid to acquire real estate ventures														$ 12,800,000
Equity method investment percentage of interests acquired by the Company and HSRE														30.00%
Construction Loan													$ 97,800,000
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
Indebtedness to third parties, refinanced amount													$ 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%
51 N 50 Patterson [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method																								$ 21,368,000					$ 21,368,000		21,212,000
Equity method investment percentage																70.00%								70.00%	[4]				70.00%	[4]
Real estate ventures aggregate indebtedness to third parties																								$ 0					$ 0		0
Payments to Acquire Land																$ 15,200,000
Area owned by real estate venture of undeveloped parcels of land | a																0.9
51 N 50 Patterson [Member] | JBG [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage																30.00%
Payments to Acquire Land																$ 6,500,000
1250 First Street Office [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method																								$ 17,838,000					$ 17,838,000		17,867,000
Equity method investment percentage																70.00%								70.00%	[4]				70.00%	[4]
Real estate ventures aggregate indebtedness to third parties																								$ 0					$ 0		0
Payments to Acquire Land																$ 13,200,000
Area owned by real estate venture of undeveloped parcels of land | a																0.5
1250 First Street Office [Member] | JBG [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage																30.00%
Payments to Acquire Land																$ 5,700,000
4040 Wilson Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	[9]																							$ 37,371,000					$ 37,371,000		37,179,000
Equity method investment percentage																								50.00%	[4],[9]				50.00%	[4],[9]			50.00%
Real estate ventures aggregate indebtedness to third parties	[9]																							$ 57,288,000					$ 57,288,000		6,664,000
Area owned by real estate venture of undeveloped parcels of land | a																							1.3
Secured construction loan with total borrowing capacity																								150,000,000					150,000,000		150,000,000
Advanced under the construction loan																													57,300,000
Guarantees, maximum exposure amount																								41,300,000					41,300,000
4040 Wilson Venture [Member] | Mixed Use Property [Member]
Schedule Of Equity Method Investments [Line Items]
Area of Real Estate Property | ft²																							427,500
Number of Properties | property																							8
4040 Wilson Venture [Member] | Brandywine Realty Trust [Member]
Schedule Of Equity Method Investments [Line Items]
Cash paid to acquire real estate ventures																							$ 36,000,000
Capital contribution to venture																								36,900,000					36,900,000
4040 Wilson Venture [Member] | Ashton Park [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage																							50.00%
Capital contribution to venture																								36,900,000					36,900,000
PJP VII [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method																								$ 1,100,000					$ 1,100,000		1,156,000
Equity method investment percentage	[4]																							25.00%					25.00%
Real estate ventures aggregate indebtedness to third parties																								$ 3,777,000					$ 3,777,000		$ 4,792,000
Construction loan, principal amount																								3,800,000					3,800,000
Guarantees, maximum exposure amount																								$ 300,000					$ 300,000
[1]	Gain/(Loss) on Sale is net of closing and other transaction related costs.
[2]	See “ Brandywine - AI Venture: Other Than Temporary Impairment” section below
[3]	See “ Brandywine - AI Venture: Station Square and 7101 Wisconsin Avenu e” and “ Brandywine - AI Venture: Other Than Temporary Impairment” sections below for information discussing activity that occurred during 2018 and 2017 relating to this venture.
[4]	Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable.
[5]	On August 1, 2018, the MAP Venture refinanced its $180.8 million third party debt financing, secured by the buildings of MAP Venture and maturing February 9, 2019, with $185.0 million third party debt financing, also secured by the buildings, bearing interest at LIBOR + 2.45% capped at a total maximum interest of 6.00% and maturing on August 1, 2023.
[6]	The basis difference associated with this venture is allocated between cost and the underlying equity in the net assets of the investee and is accounted for as if the entity were consolidated (i.e., allocated to the Company’s relative share of assets and liabilities with an adjustment to recognize equity in earnings for the appropriate depreciation/amortization).
[7]	On January 5, 2018, the Company exchanged its 20% interest in Seven Tower Bridge to acquire the remaining 35% interest in Four Tower Bridge. For further information regarding the accounting of the transaction, see “ Four Tower Bridge Acquisition
[8]	On January 10, 2018, HSRE-BDN I, LLC (evo at Cira Centre South) sold the 345-unit student housing tower, its sole operating asset. See “ evo at Cira Disposition
[9]	During the fourth quarter of 2017, 4040 Wilson obtained a secured construction loan with a total borrowing capacity of $150.0 million.

Investment in Unconsolidated _4

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, 2018		Dec. 31, 2017		Dec. 31, 2016	Jun. 26, 2018	Jan. 05, 2018	May 29, 2015	Jan. 20, 2011
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method		$ 169,100		$ 194,621		$ 281,331
Company’s share of income (loss) (Company’s basis)		(15,231)		(8,306)		$ (11,503)
Equity Method Investment Summarized Financial Information Debt		$ 370,319		$ 768,912
Brandywine - AI Venture LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage		50.00%	[1],[2]	50.00%		50.00%
Investment in Real Estate Ventures, equity method	[2]	$ 11,731		$ 43,560
Company’s share of income (loss) (Company’s basis)		(14,559)	[2]	(4,465)	[2]	$ (5,895)
Equity Method Investment Summarized Financial Information Debt	[2]	$ 26,111		93,117
Debt Instrument, Interest Rate, Effective Percentage	[2]	4.65%
Rockpoint Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage	[1],[3]	15.00%
Investment in Real Estate Ventures, equity method	[3]	$ 47,834		0
Company’s share of income (loss) (Company’s basis)	[3]	83		0
Equity Method Investment Summarized Financial Information Debt	[3]	$ 0		0
MAP Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage	[1],[4]	50.00%
Investment in Real Estate Ventures, equity method	[4]	$ 11,173		15,450
Company’s share of income (loss) (Company’s basis)	[4]	(2,155)		(3,443)
Equity Method Investment Summarized Financial Information Debt	[4]	$ 185,000		180,800
Debt Instrument, Interest Rate Terms	[4]	L+2.45%
Debt Instrument, Maturity Date, Month and Year	[4]	2023-08
Four Tower Bridge [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage		65.00%	[1],[5]					35.00%
Investment in Real Estate Ventures, equity method	[5]	$ 0		3,032
Company’s share of income (loss) (Company’s basis)	[5]	0		746
Equity Method Investment Summarized Financial Information Debt	[5]	$ 0		9,749
PJP VII [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage	[1]	25.00%
Investment in Real Estate Ventures, equity method		$ 1,100		1,156
Company’s share of income (loss) (Company’s basis)		157		175
Equity Method Investment Summarized Financial Information Debt		$ 3,777		4,792
Debt Instrument, Interest Rate Terms		L+2.65%
Debt Instrument, Maturity Date, Month and Year		2019-12
PJP Two [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage	[1]	30.00%
Investment in Real Estate Ventures, equity method		$ 663		604
Company’s share of income (loss) (Company’s basis)		179		72
Equity Method Investment Summarized Financial Information Debt		$ 2,214		2,564
Debt Instrument, Interest Rate, Effective Percentage		6.12%
Debt Instrument, Maturity Date, Month and Year		2023-11
PJP VI [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage	[1]	25.00%
Investment in Real Estate Ventures, equity method		$ 125		179
Company’s share of income (loss) (Company’s basis)		71		38
Equity Method Investment Summarized Financial Information Debt		$ 7,069		7,370
Debt Instrument, Interest Rate, Effective Percentage		6.08%
Debt Instrument, Maturity Date, Month and Year		2023-04
DRA Austin Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage	[1],[6]	50.00%
Investment in Real Estate Ventures, equity method	[6]	$ 0		13,972
Company’s share of income (loss) (Company’s basis)	[6]	1,687		(989)
Equity Method Investment Summarized Financial Information Debt	[6]	$ 0		249,481
Brandywine 1919 Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage		50.00%	[1],[7]				50.00%			50.00%
Investment in Real Estate Ventures, equity method	[7]	$ 19,897		22,268
Company’s share of income (loss) (Company’s basis)	[7]	253		(194)
Equity Method Investment Summarized Financial Information Debt	[7]	$ 88,860		88,860
Debt Instrument, Interest Rate, Effective Percentage	[7]	4.00%
Debt Instrument, Maturity Date, Month and Year	[7]	2023-06
HSRE BDN I, LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage	[1]	50.00%
Investment in Real Estate Ventures, equity method		$ 0		17,671
Company’s share of income (loss) (Company’s basis)		(358)		449
Equity Method Investment Summarized Financial Information Debt		0		110,886
TB-BDN Plymouth Apartments [Member]
Schedule Of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	[8]	0		0
Company’s share of income (loss) (Company’s basis)	[8]	0		99
Equity Method Investment Summarized Financial Information Debt	[8]	$ 0		0
4040 Wilson Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage		50.00%	[1],[9]			50.00%
Investment in Real Estate Ventures, equity method	[9]	$ 37,371		37,179
Company’s share of income (loss) (Company’s basis)	[9]	(192)		(255)
Equity Method Investment Summarized Financial Information Debt	[9]	$ 57,288		6,664
Debt Instrument, Interest Rate Terms	[9]	L+2.75%
Debt Instrument, Maturity Date, Month and Year	[9]	2021-12
51 N 50 Patterson [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage		70.00%	[1]						70.00%
Investment in Real Estate Ventures, equity method		$ 21,368		21,212
Company’s share of income (loss) (Company’s basis)		(137)		(176)
Equity Method Investment Summarized Financial Information Debt		$ 0		0
Seven Tower Bridge [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage	[1],[5]	20.00%
Investment in Real Estate Ventures, equity method	[5]	$ 0		471
Company’s share of income (loss) (Company’s basis)	[5]	0		(214)
Equity Method Investment Summarized Financial Information Debt	[5]	$ 0		14,629
1250 First Street Office [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage		70.00%	[1]						70.00%
Investment in Real Estate Ventures, equity method		$ 17,838		17,867
Company’s share of income (loss) (Company’s basis)		(260)		(149)
Equity Method Investment Summarized Financial Information Debt		$ 0		$ 0
[1]	Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable.
[2]	See “ Brandywine - AI Venture: Station Square and 7101 Wisconsin Avenu e” and “ Brandywine - AI Venture: Other Than Temporary Impairment” sections below for information discussing activity that occurred during 2018 and 2017 relating to this venture.
[3]	On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment, known as the Rockpoint Portfolio, to a newly-formed joint venture, known as the Herndon Innovation Center Metro Portfolio Venture, LLC, for a gross sales price of $312.0 million. Rockpoint and the Company own 85% and 15% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. See “ Herndon Innovation Center Metro Portfolio Venture, LLC ” section below for further details.
[4]	On August 1, 2018, the MAP Venture refinanced its $180.8 million third party debt financing, secured by the buildings of MAP Venture and maturing February 9, 2019, with $185.0 million third party debt financing, also secured by the buildings, bearing interest at LIBOR + 2.45% capped at a total maximum interest of 6.00% and maturing on August 1, 2023.
[5]	On January 5, 2018, the Company exchanged its 20% interest in Seven Tower Bridge to acquire the remaining 35% interest in Four Tower Bridge. For further information regarding the accounting of the transaction, see “ Four Tower Bridge Acquisition
[6]	See “ Austin Venture ” section below for information discussing the Company’s purchase of its partner’s entire 50 % interest in the twelve remaining properties within the Austin Venture on December 11, 2018.
[7]	The basis difference associated with this venture is allocated between cost and the underlying equity in the net assets of the investee and is accounted for as if the entity were consolidated (i.e., allocated to the Company’s relative share of assets and liabilities with an adjustment to recognize equity in earnings for the appropriate depreciation/amortization).
[8]	On January 31, 2017, the Company sold its 50% interest in TB-BDN Plymouth Apartments, LP.
[9]	During the fourth quarter of 2017, 4040 Wilson obtained a secured construction loan with a total borrowing capacity of $150.0 million.

Investment in Unconsolidated _5

Investment in Unconsolidated Real Estate Ventures - Investment in Real Estate Ventures and Share of Real Estate Ventures' Income (Loss) (Parenthetical) (Details) $ in Thousands

Dec. 28, 2018USD ($)property

Aug. 01, 2018USD ($)

Jun. 26, 2018USD ($)

Jan. 31, 2017USD ($)property

Dec. 31, 2018USD ($)ft²property

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 20, 2018USD ($)ft²property

Dec. 11, 2018ft²property

Sep. 30, 2018property

Jan. 05, 2018

Oct. 21, 2014

Jan. 20, 2011

Schedule Of Equity Method Investments [Line Items]

Repayment of mortgage debt

$ 122,180

$ 4,931

$ 357,151

Number of Properties Sold | property

10

Area of Real Estate Property | ft²

16,777,249

Gross sales price

$ 359,300

Equity Method Investment Summarized Financial Information Debt

$ 370,319

768,912

Number of Properties acquired | property

97

Debt, net

$ 365,707

766,420

Mortgage notes payable, net

$ 320,869

$ 317,216

DRA Austin Venture [Member]

Schedule Of Equity Method Investments [Line Items]

Area of Real Estate Property | ft²

1,570,123

Equity method investment percentage

50.00%

Percentage of ownership interests

50.00%

Number of Properties acquired | property

12

Metropolitan Washington, D.C. - Office [Member]

Schedule Of Equity Method Investments [Line Items]

Number of properties contributed to a joint venture | property

8

TB-BDN Plymouth Apartments [Member]

Schedule Of Equity Method Investments [Line Items]

Number of Properties Sold | property

398

Gross sales price

$ 100,500

Percentage of ownership interests

50.00%

Sale of ownership interest percentage

50.00%

Brandywine - AI Venture [Member]

Schedule Of Equity Method Investments [Line Items]

Equity method investment percentage

50.00%

[1],[2]

50.00%

50.00%

Equity Method Investment Summarized Financial Information Debt

[2]

$ 26,111

$ 93,117

Debt Instrument, Interest Rate, Effective Percentage

[2]

4.65%

Debt, net

$ 26,020

92,917

Herndon Innovation Center Metro Portfolio Venture, LLC [Member] | Metropolitan Washington, D.C. - Office [Member]

Schedule Of Equity Method Investments [Line Items]

Number of properties contributed to a joint venture | property

8

Area of Real Estate Property | ft²

1,293,197

Gross sales price

$ 312,000

Equity method investment percentage

15.00%

Herndon Innovation Center Metro Portfolio Venture, LLC [Member] | Metropolitan Washington, D.C. - Office [Member] | Rockpoint [Member]

Schedule Of Equity Method Investments [Line Items]

Equity method investment percentage

85.00%

MAP Ground Lease Venture LLC [Member]

Schedule Of Equity Method Investments [Line Items]

Debt Instrument Maturity Date

Feb. 9, 2019

Equity Method Investment Summarized Financial Information Debt

$ 180,800

Seven Tower Bridge [Member]

Schedule Of Equity Method Investments [Line Items]

Equity method investment percentage

[1],[3]

20.00%

Equity Method Investment Summarized Financial Information Debt

[3]

$ 0

14,629

Sale of ownership interest percentage

20.00%

Four Tower Bridge [Member]

Schedule Of Equity Method Investments [Line Items]

Equity method investment percentage

65.00%

[1],[3]

35.00%

Equity Method Investment Summarized Financial Information Debt

[3]

$ 0

9,749

1919 Ventures [Member]

Schedule Of Equity Method Investments [Line Items]

Equity method investment percentage

50.00%

50.00%

[1],[4]

50.00%

Equity Method Investment Summarized Financial Information Debt

[4]

$ 88,860

88,860

Debt Instrument, Interest Rate, Effective Percentage

[4]

4.00%

Debt, net

$ 44,400

Note receivable

$ 44,400

Loan interest rate

4.00%

Mortgage loans scheduled maturity date

Jun. 25, 2023

Repayment of construction loan

$ 88,800

Construction loan, principal amount

88,600

Accrued interest on construction loan

200

1919 Ventures [Member] | LCOR/CalSTRS [Member]

Schedule Of Equity Method Investments [Line Items]

Equity method investment percentage

50.00%

Debt, net

44,400

1919 Ventures [Member] | Other Assets [Member]

Schedule Of Equity Method Investments [Line Items]

Note receivable

$ 44,400

4040 Wilson Venture [Member]

Schedule Of Equity Method Investments [Line Items]

Equity method investment percentage

50.00%

[1],[5]

50.00%

Equity Method Investment Summarized Financial Information Debt

[5]

$ 57,288

6,664

Mortgage notes payable, net

$ 150,000

Secured JV Debt [Member] | Brandywine - AI Venture [Member]

Schedule Of Equity Method Investments [Line Items]

Debt Instrument, Interest Rate, Stated Percentage

3.22%

Debt Instrument, Number of Fixed Rate Mortgages

1

Repayment of mortgage debt

$ 66,500

Number of Properties Sold | property

3

Secured JV Debt [Member] | Brandywine - AI Venture [Member] | Fixed rate loan maturing January 1, 2022 [Member]

Schedule Of Equity Method Investments [Line Items]

Debt Instrument, Face Amount

$ 26,100

Debt Instrument, Interest Rate, Stated Percentage

4.65%

Debt Instrument Maturity Date

Jan. 1, 2022

Secured Debt [Member] | MAP Ground Lease Venture LLC [Member]

Schedule Of Equity Method Investments [Line Items]

Debt Instrument, Face Amount

$ 185,000

Debt Instrument Maturity Date

Aug. 1, 2023

Debt instrument, basis spread on variable rate

2.45%

Secured Debt [Member] | MAP Ground Lease Venture LLC [Member] | Maximum [Member]

Schedule Of Equity Method Investments [Line Items]

Debt Instrument, Interest Rate, Effective Percentage

6.00%

[1]

Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable.

[2]

See “ Brandywine - AI Venture: Station Square and 7101 Wisconsin Avenu e” and “ Brandywine - AI Venture: Other Than Temporary Impairment” sections below for information discussing activity that occurred during 2018 and 2017 relating to this venture.

[3]

On January 5, 2018, the Company exchanged its 20% interest in Seven Tower Bridge to acquire the remaining 35% interest in Four Tower Bridge. For further information regarding the accounting of the transaction, see “ Four Tower Bridge Acquisition

[4]

The basis difference associated with this venture is allocated between cost and the underlying equity in the net assets of the investee and is accounted for as if the entity were consolidated (i.e., allocated to the Company’s relative share of assets and liabilities with an adjustment to recognize equity in earnings for the appropriate depreciation/amortization).

[5]

During the fourth quarter of 2017, 4040 Wilson obtained a secured construction loan with a total borrowing capacity of $150.0 million.

Investment in Unconsolidated _6

Investment in Unconsolidated Real Estate Ventures - Summary of Financial Position of Real Estate Ventures (Details) - USD ($) $ in Thousands		Dec. 31, 2018		Dec. 31, 2017
Schedule Of Equity Method Investments [Line Items]
Net property		$ 835,983		$ 1,083,965
Other assets		159,499		161,932
Other liabilities		85,681		97,707
Debt, net		365,707		766,420
Equity	[1]	544,094		381,770
DRA Austin Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		0	[2]	263,557
Other assets		0	[2]	42,272
Other liabilities		0	[2]	24,131
Debt, net		0	[2]	248,700
Equity	[1]	0	[2]	32,998
Brandywine - AI Venture LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		47,043		158,960
Other assets		11,206		24,181
Other liabilities		2,002		4,493
Debt, net		26,020		92,917
Equity	[1]	30,227		85,731
evo at Cira Centre South Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		0	[3]	143,990
Other assets		0	[3]	8,563
Other liabilities		0	[3]	1,648
Debt, net		0	[3]	110,136
Equity	[1]	0	[3]	40,769
Other Income [Member]
Schedule Of Equity Method Investments [Line Items]
Net property		788,940		517,458
Other assets		148,293		86,916
Other liabilities		83,679		67,435
Debt, net		339,687		314,667
Equity	[1]	$ 513,867		$ 222,272
[1]	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.
[2]	On December 11, 2018, the Company acquired DRA’s 50% ownership interest in the DRA Austin Venture for an aggregate purchase price of $535.1 million. See “Austin Venture”
[3]	On January 10, 2018, HSRE-BDN I, LLC (evo at Cira Centre South) sold the 345-unit student housing tower, its sole operating asset. See “ evo at Cira Disposition

Investment in Unconsolidated _7

Investment in Unconsolidated Real Estate Ventures - Summary of Financial Position of Real Estate Ventures (Parenthetical) (Details) $ in Millions	Dec. 11, 2018USD ($)	Jan. 10, 2018property
Evo at Cira Disposition [Member]
Schedule Of Equity Method Investments [Line Items]
Number of property units sold | property		345
DRA Austin Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Percentage of ownership interests	50.00%
Aggregate purchase price | $	$ 535.1

Investment in Unconsolidated _8

Investment in Unconsolidated Real Estate Ventures - Summary of Results of Operations of Real Estate Ventures with Interests (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016		Mar. 02, 2016	Jan. 25, 2013
Schedule Of Equity Method Investments [Line Items]
Equity in income (loss) of Real Estate Ventures			$ (15,231)		$ (8,306)		$ (11,503)
DRA Austin Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue			53,476		85,500		85,749
Operating expenses			(22,994)		(35,997)		(37,643)
Interest expense, net			(9,083)		(13,985)		(15,052)
Depreciation and amortization			(19,226)		(34,026)		(38,365)
Provision for impairment			0				0	[1]
Loss on extinguishment of debt			(356)		(2,613)
Net income (loss)			$ 1,817		$ (1,121)		$ (5,311)	[2]
Ownership interest %			50.00%		50.00%		50.00%
Company's share of net income (loss)			$ 909		$ (560)		$ (2,656)
Other-than-temporary impairment	[3]		0		0
Basis adjustments and other			778		(429)		776
Equity in income (loss) of Real Estate Ventures			1,687		(989)		(1,880)
Brandywine - AI Venture LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue			23,515		29,500		31,047
Operating expenses			(10,483)		(12,298)		(13,654)
Interest expense, net			(3,478)		(4,707)		(5,825)
Depreciation and amortization			(8,991)		(11,428)		(12,811)
Provision for impairment			(20,832)				(10,476)	[1]
Loss on extinguishment of debt			(695)		(811)
Net income (loss)			$ (20,964)		$ 256		$ (11,719)	[2]
Ownership interest %			50.00%	[4],[5]	50.00%		50.00%
Company's share of net income (loss)			$ (10,482)		$ 128		$ (5,860)
Other-than-temporary impairment		$ (4,800)	(4,076)	[3]	(4,844)	[3]
Basis adjustments and other			(1)		251		(35)
Equity in income (loss) of Real Estate Ventures			(14,559)	[5]	(4,465)	[5]	(5,895)
evo at Cira Centre South Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue			163		12,285		12,393
Operating expenses			(256)		(3,075)		(3,183)
Interest expense, net			(123)		(4,092)		(3,230)
Depreciation and amortization			(409)		(4,512)		(4,512)
Provision for impairment			0				0	[1]
Loss on extinguishment of debt			0		0
Net income (loss)			$ (625)		$ 606		$ 1,468	[2]
Ownership interest %			50.00%		50.00%		50.00%		50.00%	30.00%
Company's share of net income (loss)			$ (313)		$ 303		$ 734
Other-than-temporary impairment	[3]		0		0
Basis adjustments and other			(45)		146		109
Equity in income (loss) of Real Estate Ventures			(358)		449		843
Other Income [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue			88,172		88,986		85,263
Operating expenses			(48,302)		(47,970)		(48,712)
Interest expense, net			(17,090)		(17,429)		(16,207)
Depreciation and amortization			(25,200)		(28,474)		(30,050)
Provision for impairment			0				0	[1]
Loss on extinguishment of debt			(334)		0
Net income (loss)			(2,754)		(4,887)		(9,706)	[2]
Company's share of net income (loss)			(2,038)		(1,735)		(4,719)
Other-than-temporary impairment	[3]		0		0
Basis adjustments and other			37		(1,566)		148
Equity in income (loss) of Real Estate Ventures			(2,001)		(3,301)		(4,571)
Unconsolidated Real Estate Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue			165,326		216,271		214,452
Operating expenses			(82,035)		(99,340)		(103,192)
Interest expense, net			(29,774)		(40,213)		(40,314)
Depreciation and amortization			(53,826)		(78,440)		(85,738)
Provision for impairment			(20,832)				(10,476)	[1]
Loss on extinguishment of debt			(1,385)		(3,424)
Net income (loss)			(22,526)		(5,146)		(25,268)	[2]
Company's share of net income (loss)			(11,924)		(1,864)		(12,501)
Other-than-temporary impairment	[3]		(4,076)		(4,844)
Basis adjustments and other			769		(1,598)		998
Equity in income (loss) of Real Estate Ventures			$ (15,231)		$ (8,306)		$ (11,503)
[1]	See “ Brandywine - AI Venture: Station Square Impairment”
[2]	During the year ended December 31, 2016, there were $7.1 million of acquisition deal costs related to the formation of the MAP Venture.
[3]	See “ Brandywine - AI Venture: Other Than Temporary Impairment” section below
[4]	Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable.
[5]	See “ Brandywine - AI Venture: Station Square and 7101 Wisconsin Avenu e” and “ Brandywine - AI Venture: Other Than Temporary Impairment” sections below for information discussing activity that occurred during 2018 and 2017 relating to this venture.

Investment in Unconsolidated _9

Investment in Unconsolidated Real Estate Ventures - Summary of Results of Operations of Real Estate Ventures with Interests (Parenthetical) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
MAP Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Acquisition deal costs	$ 7.1

Investment in Unconsolidated_10

Investment in Unconsolidated Real Estate Ventures - Aggregate Principal Payments of Recourse and Non-recourse Debt Payable to Third-parties (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Equity Method Investments [Line Items]
2,019	$ 7,595
2,020	87,226
2,021	15,143
2,022	348,832
2,023	556,736
Thereafter	1,028,610
Total principal payments	370,319	$ 768,912
Net deferred financing costs	(10,241)
Outstanding indebtedness	365,707	$ 766,420
Unconsolidated Real Estate Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
2,019	4,998
2,020	1,290
2,021	58,651
2,022	25,277
2,023	280,005
Thereafter	98
Total principal payments	370,319
Net deferred financing costs	(4,612)
Outstanding indebtedness	$ 365,707

Investment in Unconsolidated_11

Investment in Unconsolidated Real Estate Ventures - Summary of Transaction (Details) - USD ($) $ in Thousands	Oct. 18, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 17, 2017
Schedule Of Equity Method Investments [Line Items]
Gross sales price		$ 359,300
Debt principal		(370,319)	$ (768,912)
Cash to Austin Venture		60,346	145,416	$ 21,022
Company's share of gain		$ 142,233	$ 80,526	$ 20,000
Austin Joint Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Gross sales price	$ 333,250
Debt principal	(150,968)				$ (151,000)
Debt prepayment penalties	(2,120)
Closing costs and net prorations	(7,420)
Cash to Austin Venture	$ 172,742
Ownership percentage	50.00%
Cash to the Company	$ 86,371
Austin Venture basis of sold properties	(92,559)
Austin Venture gain on sale	80,183
Company's share of gain	40,092
Deferred gain on sale	12,072
Gain on real estate venture transactions	$ 52,164

Deferred Costs - Deferred Costs

Deferred Costs - Deferred Costs (Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Components of Deferred Costs Net [Abstract]
Leasing costs, Total Cost	$ 144,831	$ 154,481
Total Cost	151,129	158,076
Leasing costs, Accumulated Amortization	(56,846)	(59,046)
Total, Accumulated Amortization	(60,054)	(61,381)
Leasing costs, Deferred Costs, net	87,985	95,435
Financing costs, Deferred Costs, net	10,241
Deferred Costs	91,075	96,695
Revolving Credit Facility [Member]
Components of Deferred Costs Net [Abstract]
Financing costs, Total Cost	6,298	3,595
Financing costs, Accumulated Amortization	(3,208)	(2,335)
Financing costs, Deferred Costs, net	$ 3,090	$ 1,260

Deferred Costs (Textual) (Detai

Deferred Costs (Textual) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs (Textual) [Abstract]
Capitalized internal direct leasing costs	$ 3.9	$ 4.6	$ 5

Intangible Assets - Intangible

Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets [Line Items]
Intangible Assets, Total Cost	$ 196,417	$ 123,806
Intangible Assets, Accumulated Amortization	(65,069)	(58,834)
Intangible Assets, net	131,348	64,972
Acquired Lease Intangibles, Net	31,783	20,274
Below market leases [Member]
Intangible Assets [Line Items]
Acquired Lease Intangibles, Gross	49,655	36,213
Acquired Lease Intangibles, Accumulated Amortization	(17,872)	(15,939)
Acquired Lease Intangibles, Net	31,783	20,274
In-place lease value [Member]
Intangible Assets [Line Items]
Intangible Assets, Total Cost	181,887	108,060
Intangible Assets, Accumulated Amortization	(53,376)	(47,003)
Intangible Assets, net	128,511	61,057
Tenant relationship value [Member]
Intangible Assets [Line Items]
Intangible Assets, Total Cost	9,564	11,201
Intangible Assets, Accumulated Amortization	(8,551)	(9,275)
Intangible Assets, net	1,013	1,926
Above market leases acquired [Member]
Intangible Assets [Line Items]
Intangible Assets, Total Cost	4,966	4,545
Intangible Assets, Accumulated Amortization	(3,142)	(2,556)
Intangible Assets, net	$ 1,824	$ 1,989

Intangible Assets (Textual) (De

Intangible Assets (Textual) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Tenant Move-Outs Prior to End of the Lease Term [Member]
Finite Lived Intangible Assets [Line Items]
Intangible Assets Written Off Through Accelerated Amortization	$ 0.7	$ 0.6	$ 0.6

Intangible Assets and Liabiliti

Intangible Assets and Liabilities - Annual Amortization of Intangible Assets, Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets
2,019	$ 41,968
2,020	28,393
2,021	20,128
2,022	12,791
2,023	9,756
Thereafter	18,312
Intangible Assets, net	131,348	$ 64,972
Liabilities
2,019	7,403
2,020	5,707
2,021	4,302
2,022	2,654
2,023	2,094
Thereafter	9,623
Acquired Lease Intangibles, Net	$ 31,783	$ 20,274

Debt Obligations - Consolidated

Debt Obligations - Consolidated Debt Obligations Outstanding (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Nov. 09, 2017
Consolidated debt obligations
Plus: premiums/(discounts), net		$ (5,855)
Net deferred financing costs		(10,241)
Total Debt Obligations		2,028,046	$ 1,930,828
Secured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		323,032	320,107
Plus: premiums/(discounts), net		(1,759)	(2,325)
Net deferred financing costs		(404)	(566)
Total mortgage indebtedness		320,869	317,216
Secured Debt [Member] | Two Logan Square [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 82,805	84,440
Effective interest rate		3.98%
Debt instrument maturity date		May 1, 2020
Secured Debt [Member] | Four Tower Bridge [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 9,526	0
Effective interest rate	[1]	4.50%
Debt instrument maturity date		Feb. 28, 2021
Secured Debt [Member] | One Commerce Square [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 120,183	123,667
Effective interest rate		3.64%
Debt instrument maturity date		Apr. 5, 2023
Secured Debt [Member] | Two Commerce Square [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 110,518	112,000
Effective interest rate		4.51%
Debt instrument maturity date		Apr. 5, 2023
Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 1,721,110	1,628,610
Plus: premiums/(discounts), net		(4,096)	(4,423)
Net deferred financing costs		(9,837)	(10,575)
Total unsecured indebtedness		1,707,177	1,613,612
Unsecured Debt [Member] | $600 million Unsecured Credit Facility [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 92,500	0
Debt instrument, description of variable rate basis		LIBOR + 1.10%
Spread on variable rate		1.10%
Debt instrument maturity date		Jul. 15, 2022
Unsecured Debt [Member] | Seven Year Term Loan - Swapped to fixed [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 250,000	250,000
Effective interest rate	[2]	2.87%
Debt instrument maturity date		Oct. 8, 2022
Unsecured Debt [Member] | $350M 3.95% Guaranteed Notes due 2023 [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 350,000	350,000
Effective interest rate		3.87%
Debt instrument maturity date		Apr. 15, 2018
Unsecured Debt [Member] | $250.0M 4.10% Guaranteed Notes due 2024 [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 250,000	250,000
Effective interest rate		4.33%
Debt instrument maturity date		Feb. 15, 2023
Unsecured Debt [Member] | $450.0M 3.95% Guaranteed Notes due 2027 [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 450,000	450,000	$ 450,000
Effective interest rate		4.03%
Debt instrument maturity date		Oct. 1, 2024
Unsecured Debt [Member] | $250M 4.55% Guaranteed Notes due 2029 [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 250,000	250,000
Effective interest rate		4.60%
Debt instrument maturity date		Oct. 1, 2029
Unsecured Debt [Member] | Indenture IA (Preferred Trust I) [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 27,062	27,062
Debt instrument, description of variable rate basis		LIBOR + 1.25%
Spread on variable rate		1.25%
Debt instrument maturity date		Mar. 30, 2035
Unsecured Debt [Member] | Indenture IB (Preferred Trust I) - Swapped to fixed [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 25,774	25,774
Effective interest rate		3.30%
Debt instrument maturity date		Apr. 30, 2035
Unsecured Debt [Member] | Indenture II (Preferred Trust II) - Swapped to fixed [Member]
Consolidated debt obligations
Long-term Debt, Gross		$ 25,774	$ 25,774
Effective interest rate		3.09%
Debt instrument maturity date		Jul. 30, 2035
[1]	This loan was assumed upon acquisition of the related property on January 5, 2018. The interest rate reflects the market rate at the time of acquisition.
[2]	On December 13, 2018, the Company amended and restated its $250.0 million seven-year term loan maturing October 8, 2022. In connection with the terms of the amendment, the credit spread on the term loan decreased from LIBOR plus 1.80% to LIBOR plus 1.25%, reducing the Company’s effective interest rate by 0.55%. Through a series of interest rate swaps, the $250.0 million outstanding balance of the term loan has a fixed interest rate of 2.87%.

Debt Obligations - Consolidat_2

Debt Obligations - Consolidated Debt Obligations Outstanding (Parenthetical) (Details) - Unsecured Debt [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 1,721,110	$ 1,628,610
$600 million Unsecured Credit Facility [Member]
Debt Instrument [Line Items]
Unsecured credit facility, maximum borrowing capacity		600,000
Long-term Debt, Gross		$ 92,500	0
Debt Instrument Maturity Date		Jul. 15, 2022
Debt Instrument, Credit Spread		LIBOR + 1.10%
Seven Year Term Loan - Swapped to fixed [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 250,000	$ 250,000
Debt Instrument Maturity Date		Oct. 8, 2022
Decrease in interest rate		(0.55%)
Effective interest rate	[1]	2.87%
Seven Year Term Loan - Swapped to fixed [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Credit Spread		LIBOR plus 1.80%
Seven Year Term Loan - Swapped to fixed [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Credit Spread		LIBOR plus 1.25%
[1]	On December 13, 2018, the Company amended and restated its $250.0 million seven-year term loan maturing October 8, 2022. In connection with the terms of the amendment, the credit spread on the term loan decreased from LIBOR plus 1.80% to LIBOR plus 1.25%, reducing the Company’s effective interest rate by 0.55%. Through a series of interest rate swaps, the $250.0 million outstanding balance of the term loan has a fixed interest rate of 2.87%.

Debt Obligations (Textual) (Det

Debt Obligations (Textual) (Details)	Jul. 17, 2018USD ($)Extension	Dec. 18, 2017USD ($)	Nov. 16, 2017USD ($)	Nov. 09, 2017USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Line of Credit					$ 92,500,000	$ 0
Loss on early extinguishment of debt					(105,000)	(3,933,000)	$ (66,590,000)
Extinguishment of Debt, Amount					$ 0	$ 325,000,000	$ 0
Prior Revolving Credit Facilty [Member]
Debt Instrument [Line Items]
Debt instrument maturity date	May 15, 2019
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate					3.24%	2.28%
Line of Credit					$ 92,500,000	$ 0
Effective interest rate on credit facility					3.61%
Interest expense borrowings					$ 1,000,000	$ 2,600,000
Revolving Credit Facility [Member] | New Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 600,000,000
Debt instrument maturity date	Jul. 15, 2022
Debt instrument, number of extensions | Extension	2
Debt instrument, maturity extension period	6 months
Debt financing costs	$ 2,700,000
Minimum Credit Spread on a LIBOR Rate Loan					0.00%
Maximum Credit Spread on a LIBOR Rate Loan					0.45%
Commitment fee percentage					0.25%
Minimum fixed charge coverage ratio					1.5
Maximum leverage ratio					0.60
Maximum unsecured indebtedness to unencumbered asset value ratio					0.60
Maximum secured indebtedness to total asset value ratio					0.40
Minimum unencumbered cash flow to interest expense on unsecured debt ratio					1.75
Maximum percent of payments of dividends and distributions					95.00%
Revolving Credit Facility [Member] | New Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Commitment fee percentage					0.125%
Revolving Credit Facility [Member] | New Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Commitment fee percentage					0.30%
Revolving Credit Facility [Member] | New Credit Facility [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Variable interest rate					1.10%
Basis spread on variable rate					1.00%
Revolving Credit Facility [Member] | New Credit Facility [Member] | LIBOR [Member] | Minimum [Member]
Debt Instrument [Line Items]
Variable interest rate					0.775%
Revolving Credit Facility [Member] | New Credit Facility [Member] | LIBOR [Member] | Maximum [Member]
Debt Instrument [Line Items]
Variable interest rate					1.45%
Revolving Credit Facility [Member] | New Credit Facility [Member] | Federal Funds Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate					0.50%
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate					4.05%	4.04%	4.03%
Long-term Debt, Gross					$ 323,032,000	$ 320,107,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross					$ 1,721,110,000	1,628,610,000
Unsecured Debt [Member] | $450.0M 3.95% Guaranteed Notes due 2027 [Member]
Debt Instrument [Line Items]
Debt instrument maturity date					Oct. 1, 2024
Long-term Debt, Gross				$ 450,000,000	$ 450,000,000	450,000,000
Debt Instrument, Interest Rate, Stated Percentage				3.95%
Debt instrument, Unamortized discount, Percent of face amount				99.25%
Debt instrument, Yield to maturity				4.04%
Debt instrument, Yield to maturity spread at time of pricing				1.70%
Treasury note rate term				10 years
Unsecured Debt [Member] | $350M 3.95% Guaranteed Notes due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument maturity date					Apr. 15, 2018
Long-term Debt, Gross					$ 350,000,000	350,000,000
Debt Instrument, Interest Rate, Stated Percentage				3.95%
Debt Instrument, Face Amount				$ 100,000,000
Debt instrument, Unamortized discount, Percent of face amount				102.497%
Debt instrument, Yield to maturity				3.40%
Debt instrument, Yield to maturity spread at time of pricing				1.40%
Treasury note rate term				5 years
Unsecured Debt [Member] | Notes 2027 and 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount						3,400,000
Debt Instrument, Unamortized Premium						$ 2,500,000
Proceeds from Notes Payable				$ 546,600,000
Unsecured Debt [Member] | Notes 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount		$ 211,600,000	$ 115,100,000
Repayments of debt			113,400,000
Repayment of prepayment penalties		2,300,000	1,200,000
Repayment of accrued interest		1,800,000	500,000
Loss on early extinguishment of debt		(2,500,000)	$ (1,400,000)
Debt instrument, cash redemption price		$ 215,700,000

Debt Obligations - Additional I

Debt Obligations - Additional Information on Repurchase of Outstanding Unsecured Notes (Details) - USD ($)		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Extinguishment Of Debt [Line Items]
Principal		$ 0	$ 325,000,000	$ 0
Repurchase Amount		0	628,590,000	149,919,000
Loss on early extinguishment of debt		(105,000)	$ (3,933,000)	$ (66,590,000)
Notes 2018 [Member]
Extinguishment Of Debt [Line Items]
Principal		325,000,000
Repurchase Amount	[1]	330,792,000
Loss on early extinguishment of debt	[2]	$ (3,933,000)
[1]	Includes prepayment penalties with respect to the redemption of debt.
[2]	Includes unamortized balance of the original issue discount and deferred financing costs.

Debt Obligations - Aggregate Sc

Debt Obligations - Aggregate Scheduled Principal Payments of Debt Obligation, Excluding Amortization of Discounts and Premiums (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
2,019	$ 7,595
2,020	87,226
2,021	15,143
2,022	348,832
2,023	556,736
Thereafter	1,028,610
Total principal payments	2,044,142
Net unamortized premiums/(discounts)	(5,855)
Net deferred financing costs	(10,241)
Total Debt Obligations	$ 2,028,046	$ 1,930,828

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Financial Instruments for which Estimates of Fair Value Differ from Carrying Amounts (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Mortgage notes payable, net		$ 320,869	$ 317,216
Note receivable		47,800	3,500
Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Note receivable	[1],[2]	47,771	3,532
Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Note receivable, fair value	[2]	47,747	3,605
Unsecured Notes Payable [Member] | Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Unsecured notes payable	[1]	1,288,024	1,286,573
Unsecured Notes Payable [Member] | Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument, fair value		1,262,570	1,314,900
Variable Rate Debt [Member] | Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Variable rate debt	[1]	419,153	327,039
Variable Rate Debt [Member] | Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument, fair value		402,924	308,872
Mortgages Notes Payable [Member] | Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Mortgage notes payable, net	[1]	320,869	317,216
Mortgages Notes Payable [Member] | Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument, fair value		$ 318,515	$ 304,665
[1]	T he carrying amounts presented in the table above are net of deferred financing costs of $7.9 million and $8.9 million for unsecured notes payable, $5.1 million and $1.3 million for variable rate debt and $0.4 million and $0.6 million for mortgage notes payable as of December 31, 2018 and December 31, 2017, respectively.
[2]	The inputs to originate the notes receivable are unobservable and, as a result, are categorized as Level 3. The Company determined fair value by calculating the present value of the cash payments to be received through the maturity date of the loans.

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Financial Instruments for which Estimates of Fair Value Differ from Carrying Amounts (Parenthetical) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deferred financing costs, net	$ 10,241
Unsecured Notes Payable [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deferred financing costs, net	9,837	$ 10,575
Unsecured Notes Payable [Member] | Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deferred financing costs, net	7,900	8,900
Variable Rate Debt [Member] | Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deferred financing costs, net	5,100	1,300
Mortgages Notes Payable [Member] | Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deferred financing costs, net	$ 400	$ 600

Fair Value of Financial Instr_5

Fair Value of Financial Instruments (Textual) (Details) - USD ($) $ in Millions	Jun. 26, 2018	Dec. 31, 2018		Jan. 20, 2011
Third Party [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Note receivable		$ 3.4
Balloon payment expected to be received at the maturity date		$ 3.1
Mortgage loans scheduled maturity date		Mar. 1, 2020
Third Party [Member] | Through March2019
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loan interest rate		7.00%
Third Party [Member] | Thereafter Until March Of2020
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loan interest rate		8.00%
1919 Ventures [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Mortgage loan	$ 44.4
Equity method investment percentage	50.00%	50.00%	[1],[2]	50.00%
Note receivable	$ 44.4
Loan interest rate	4.00%
Mortgage loans scheduled maturity date	Jun. 25, 2023
1919 Ventures [Member] | Other Assets [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Note receivable	$ 44.4
[1]	The basis difference associated with this venture is allocated between cost and the underlying equity in the net assets of the investee and is accounted for as if the entity were consolidated (i.e., allocated to the Company’s relative share of assets and liabilities with an adjustment to recognize equity in earnings for the appropriate depreciation/amortization).
[2]	Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable.

Risk Management and Use of De_3

Risk Management and Use of Derivative Financial Instruments - Terms and Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivatives Fair Value [Line Items]
Notional Amount	$ 301,548	$ 301,548
3.718% Interest Rate Swap Maturing October 8, 2022 [Member] | Cash Flow Hedging [Member]
Derivatives Fair Value [Line Items]
Derivative Asset, Notional Amount	$ 250,000	250,000
Derivative, Fixed Interest Rate	2.868%
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	$ 7,008	5,694
3.300% Interest Rate Swap Maturing January 30, 2021 [Member] | Cash Flow Hedging [Member]
Derivatives Fair Value [Line Items]
Derivative Asset, Notional Amount	$ 25,774	25,774
Derivative, Fixed Interest Rate	3.30%
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	$ 292	25
3.090% Interest Rate Swap Maturing October 30, 2019 [Member] | Cash Flow Hedging [Member]
Derivatives Fair Value [Line Items]
Derivative Asset, Notional Amount	$ 25,774	25,774
Derivative, Fixed Interest Rate	3.09%
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	$ 183	$ 59

Risk Management and Use of De_4

Risk Management and Use of Derivative Financial Instruments (Textual) (Details) - Customer	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Rent Revenue [Member] | Customer Concentration Risk [Member]
Derivatives Fair Value [Line Items]
Number of tenant accounted for 10% or more of the Company's rents	0	0	0

Limited Partners' NonControll_2

Limited Partners' NonControlling Interests in the Parent Company (Textual) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Aggregate amount related to non-controlling interests classified within equity	$ 10.1	$ 15.2
Settlement value of non controlling interest in operating partnership	$ 12.6	$ 26.9

Beneficiaries Equity of the P_3

Beneficiaries Equity of the Parent Company - Number of Shares and Net Income Used to Calculate Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator
Net income	$ 122,710	[1]	$ (43,262)	[2]	$ 13,136	$ 44,705	$ 73,844	$ 19,046	$ 7,698	$ 21,271	$ 137,289	$ 121,859	$ 40,501
Net income attributable to noncontrolling interests, Basic											(965)	(1,009)	(310)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic											(369)	(327)	(341)
Distribution to preferred shareholders											0	(2,032)	(6,900)
Preferred share redemption charge											0	(3,181)	0
Net income attributable to Common Shareholders of Brandywine Realty Trust											135,955	115,310	32,950
Net income attributable to noncontrolling interests, Diluted											(965)	(1,009)	(310)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted											(369)	(327)	(341)
Net income attributable to common shareholders, Diluted											$ 135,955	$ 115,310	$ 32,950
Denominator
Basic weighted average shares outstanding (in shares)											178,519,748	175,484,350	175,018,163
Contingent securities/Share based compensation (in shares)											1,121,744	1,323,816	992,651
Diluted weighted average shares outstanding (in shares)											179,641,492	176,808,166	176,010,814
Earnings per Common Share:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.68		$ (0.24)		$ 0.07	$ 0.25	$ 0.42	$ 0.11	$ 0.02	$ 0.11	$ 0.76	$ 0.66	$ 0.19
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.68		$ (0.24)		$ 0.07	$ 0.25	$ 0.41	$ 0.11	$ 0.02	$ 0.11	$ 0.76	$ 0.65	$ 0.19
[1]	The increase in net income for the fourth quarter primarily relates to gains of $103.8 million and $28.3 million, recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, "Real Estate Investments."
[2]	The decrease in third quarter net income primarily relates to a $56.9 million impairment charge which related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, “Real Estate Investments,”

Beneficiaries Equity of the P_4

Beneficiaries Equity of the Parent Company (Textual) (Details) - USD ($)	Dec. 31, 2018	Dec. 06, 2018	Apr. 11, 2017	Jan. 10, 2017	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 03, 2019
Class of Stock [Line Items]
Dividends, Common Stock	$ 33,600,000
Dividends payable, date to be paid	Jan. 22, 2019
Dividends payable, date of record	Jan. 8, 2019
Preferred shares authorized	20,000,000					20,000,000	20,000,000
Preferred shares outstanding	0					0	0
Preferred share redemption charge						$ 0	$ 3,181,000	$ 0
Repurchased and Retired, Shares						1,729,278	0	0
Share Price						$ 12.64
Repurchased and Retired, Value						$ 21,858,000
Common stock price per unit	$ 0.01					$ 0.01	$ 0.01	$ 0.01
Common Stock, Shares Authorized	400,000,000					400,000,000	400,000,000
Upfront costs							$ 499,000
Common shares issued under offering program								0
Cash proceeds, net of issuance costs						$ 416,000	$ 51,225,000	$ 0
Offering Program [Member]
Class of Stock [Line Items]
Common Stock, Shares Authorized				16,000,000
Upfront costs				$ 200,000
Common shares issued under offering program						23,311	2,858,991	0
Weighted average price per share	$ 18.04					$ 18.04	$ 18.19
Cash proceeds, net of issuance costs						$ 400,000	$ 51,200,000
Common shares remain available for issuance	13,117,698					13,117,698
Subsequent Event [Member]
Class of Stock [Line Items]
Authorized Amount									$ 150,000,000
Repurchased and Retired, Shares					1,337,169
Share Price					$ 12.92
Repurchased and Retired, Value					$ 17,300,000
Maximum [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Authorized Amount									$ 150,000,000
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Dividends, Common Stock		$ 33,600,000
Dividends payable, date to be paid		Jan. 22, 2019
Dividends payable, date of record		Jan. 8, 2019
Preferred share redemption charge						$ 0	3,181,000	$ 0
Repurchase program, number of common unit retired for each common share repurchased						1
Cash proceeds, net of issuance costs						$ 416,000	$ 51,225,000	$ 0
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Series E Preferred Stock [Member]
Class of Stock [Line Items]
Redemption outstanding shares			4,000,000
Redemption price per share			$ 25.51
Accrued dividends paid in cash			$ 2,000,000
Preferred share redemption charge			$ 3,200,000
Dividend Declared [Member]
Class of Stock [Line Items]
Dividends Payable, Amount Per Share	$ 0.19					$ 0.19
Dividend Declared [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Dividends Payable, Amount Per Share		$ 0.19
Redeemable Common Limited Partnership Units [Member]
Class of Stock [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share						982,871	1,479,799	1,479,799

Partners Equity of the Operat_3

Partners Equity of the Operating Partnership - Number of Units and Net Income Used to Calculate Basic and Diluted Earnings Per Common Partnership Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator
Net income	$ 122,710	[1]	$ (43,262)	[2]	$ 13,136	$ 44,705	$ 73,844	$ 19,046	$ 7,698	$ 21,271	$ 137,289	$ 121,859	$ 40,501
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic											(369)	(327)	(341)
Preferred Share distributions											0	(2,032)	(6,900)
Preferred share redemption charge											0	(3,181)	0
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted											$ (369)	$ (327)	$ (341)
Denominator
Basic weighted average shares outstanding (in shares)											178,519,748	175,484,350	175,018,163
Contingent securities/Share based compensation (in shares)											1,121,744	1,323,816	992,651
Diluted weighted average shares outstanding (in shares)											179,641,492	176,808,166	176,010,814
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.68		$ (0.24)		$ 0.07	$ 0.25	$ 0.42	$ 0.11	$ 0.02	$ 0.11	$ 0.76	$ 0.66	$ 0.19
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.68		$ (0.24)		$ 0.07	$ 0.25	$ 0.41	$ 0.11	$ 0.02	$ 0.11	$ 0.76	$ 0.65	$ 0.19
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Net income	$ 122,710	[1]	$ (43,262)	[2]	$ 13,136	$ 44,705	$ 73,844	$ 19,046	$ 7,698	$ 21,271	$ 137,289	$ 121,859	$ 40,501
Net income attributable to noncontrolling interests											(55)	(29)	(15)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic											(369)	(327)	(341)
Preferred Share distributions											0	(2,032)	(6,900)
Preferred share redemption charge											0	(3,181)	0
Net income attributable to common unitholders, Basic											136,865	116,290	33,245
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted											(369)	(327)	(341)
Net income attributable to common unitholders, Diluted											$ 136,865	$ 116,290	$ 33,245
Denominator
Basic weighted average shares outstanding (in shares)											179,959,370	176,964,149	176,523,800
Contingent securities/Share based compensation (in shares)											1,121,744	1,323,816	992,651
Diluted weighted average shares outstanding (in shares)											181,081,114	178,287,965	177,516,451
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.68		$ (0.24)		$ 0.07	$ 0.25	$ 0.42	$ 0.11	$ 0.02	$ 0.11	$ 0.76	$ 0.66	$ 0.19
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.68		$ (0.24)		$ 0.07	$ 0.25	$ 0.41	$ 0.11	$ 0.02	$ 0.11	$ 0.76	$ 0.65	$ 0.19
[1]	The increase in net income for the fourth quarter primarily relates to gains of $103.8 million and $28.3 million, recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, "Real Estate Investments."
[2]	The decrease in third quarter net income primarily relates to a $56.9 million impairment charge which related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, “Real Estate Investments,”

Partners Equity of the Operat_4

Partners Equity of the Operating Partnership (Textual) (Details) - USD ($)	Dec. 31, 2018	Dec. 06, 2018	Apr. 11, 2017	Jan. 10, 2017	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 03, 2019
Earnings Per Common Partnership Unit [Line Items]
Dividends, Common Stock	$ 33,600,000
Dividends payable, date to be paid	Jan. 22, 2019
Dividends payable, date of record	Jan. 8, 2019
Preferred share redemption charge						$ 0	$ 3,181,000	$ 0
Repurchased and Retired, Shares						1,729,278	0	0
Share Price						$ 12.64
Repurchased and Retired, Value						$ 21,858,000
Common Stock, Par or Stated Value Per Share (USD per share)	$ 0.01					$ 0.01	$ 0.01	$ 0.01
Common Stock, Shares Authorized	400,000,000					400,000,000	400,000,000
Upfront costs							$ 499,000
Common shares issued under offering program								0
Cash proceeds, net of issuance costs						$ 416,000	$ 51,225,000	$ 0
Offering Program [Member]
Earnings Per Common Partnership Unit [Line Items]
Common Stock, Shares Authorized				16,000,000
Upfront costs				$ 200,000
Common shares issued under offering program						23,311	2,858,991	0
Weighted average price per share	$ 18.04					$ 18.04	$ 18.19
Cash proceeds, net of issuance costs						$ 400,000	$ 51,200,000
Common shares remain available for issuance	13,117,698					13,117,698
Subsequent Event [Member]
Earnings Per Common Partnership Unit [Line Items]
Authorized Amount									$ 150,000,000
Repurchased and Retired, Shares					1,337,169
Share Price					$ 12.92
Repurchased and Retired, Value					$ 17,300,000
Subsequent Event [Member] | Maximum [Member]
Earnings Per Common Partnership Unit [Line Items]
Authorized Amount									$ 150,000,000
Dividend Declared [Member]
Earnings Per Common Partnership Unit [Line Items]
Dividends Payable, Amount Per Share	$ 0.19					$ 0.19
Class A Units [Member]
Earnings Per Common Partnership Unit [Line Items]
Redeemable Limited Partnership Units Potential Cash Redemption Value Closing Market Price	$ 12.87					$ 12.87	$ 18.19	$ 16.51
Limited Partners' Capital Account, Units Outstanding	982,871					982,871	1,479,799	1,479,799
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings Per Common Partnership Unit [Line Items]
Preferred units outstanding	0					0	0
Dividends, Common Stock		$ 33,600,000
Dividends payable, date to be paid		Jan. 22, 2019
Dividends payable, date of record		Jan. 8, 2019
Preferred share redemption charge						$ 0	$ 3,181,000	$ 0
Repurchase program, number of mirror unit of operating partnership retired for each common share repurchased						1
Cash proceeds, net of issuance costs						$ 416,000	$ 51,225,000	$ 0
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Dividend Declared [Member]
Earnings Per Common Partnership Unit [Line Items]
Dividends Payable, Amount Per Share		$ 0.19
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Series E Preferred Stock [Member]
Earnings Per Common Partnership Unit [Line Items]
Redemption outstanding shares			4,000,000
Redemption price per share			$ 25.51
Accrued dividends paid in cash			$ 2,000,000
Preferred share redemption charge			$ 3,200,000

Share Based Compensation, 401_3

Share Based Compensation, 401(k) Plan and Deferred Compensation (Textual) (Details)	Feb. 28, 2018Installmentshares	Feb. 01, 2018shares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)	Feb. 09, 2018$ / shares	Dec. 18, 2017shares	May 18, 2017shares	Mar. 01, 2017shares	Feb. 22, 2016shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number | shares			964,359	2,238,590
Share-based compensation expense			$ 7,600,000	$ 6,300,000	$ 5,600,000
Share-based compensation expense, capitalized			1,600,000	1,200,000	1,000,000
Defined Contribution Plan, Employer Discretionary Contribution Amount			$ 400,000	500,000	400,000
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent			100.00%
Aggregate share-based awards awarded to executives | shares								6,500,000
Number of shares to be issued under deferred compensation plan included in total shares outstanding | shares			1,000,000				900,000
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense			$ 0		0
Share-based compensation expense, capitalized			0		0
Restricted Share Rights Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense			3,600,000	2,800,000	2,600,000
Share-based compensation expense, capitalized			$ 600,000	$ 400,000	400,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number | shares			466,439	455,643
Unrecognized compensation expenses			$ 1,800,000
Weighted average period over which options will be recognized			1 year 3 months 18 days
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			two to three years from the initial grant dates
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | shares			220,241
Voluntary Termination Of Employment Terms	after reaching at least age 57 and accumulating at least 15 years of service with the Company.
Accumulated Service Period For Voluntary Termination	15 years
Restricted Share Rights Awards [Member] | Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Voluntary Termination of Employment Age Limit	57 years
Restricted Share Rights Awards [Member] | Non-Officer Employees [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | shares	44,062
Number of restricted share right will get settled for common share | shares	1
Number of Vesting Installments | Installment	3
Restricted Share Rights Awards [Member] | Cliff Vest [Member] | Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | shares	134,487
Share Based Compensation Arrangement By Share Based Payment Award, Vesting Date	Apr. 15, 2021
Restricted Share Rights Awards [Member] | Installment One [Member] | Non-Officer Employees [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award, Vesting Date	Apr. 15, 2019
Restricted Share Rights Awards [Member] | Installment Two [Member] | Non-Officer Employees [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award, Vesting Date	Apr. 15, 2020
Restricted Share Rights Awards [Member] | Share-based Compensation Award, Tranche Three | Non-Officer Employees [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award, Vesting Date	Apr. 15, 2021
Restricted Share Rights Awards [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			3 years
Restricted Share Rights Awards [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			2 years
Restricted Performance Share Units Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense			$ 3,900,000	$ 3,400,000	2,800,000
Share-based compensation expense, capitalized			1,100,000	$ 800,000	600,000
Unrecognized compensation expenses			$ 2,000,000
Weighted average period over which options will be recognized			1 year 1 month 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				three-year
Common shares issued for share based compensation | shares		193,516
Dividends Payable, Amount Per Share | $ / shares						$ 0.18
Restricted Performance Share Units Plan [Member] | Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number | shares			600,273	400,488
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | shares			209,193
Aggregate share-based awards awarded to executives | shares	209,193								174,854	231,388
Restricted Performance Share Units Plan [Member] | Cliff Vest [Member] | Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights			three year cliff vesting period
Employee Share Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense			$ 100,000	$ 100,000	200,000
Share purchases made by employees under ESPP			85% of the average closing price per share for a specified period
Maximum participant contribution, percentage of compensation			20.00%
Maximum participant contribution, dollar amount			$ 50,000
Aggregate share-based awards awarded to executives | shares			1,250,000
Stock Issued During Period, Value, Employee Stock Purchase Plan			$ 500,000	$ 400,000	$ 400,000
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date			15.00%

Share Based Compensation, 401_4

Share Based Compensation, 401(k) Plan and Deferred Compensation - Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Option activity
Outstanding at beginning of year, shares	2,238,590
Exercised, shares	0
Forfeited/Expired, shares	(1,274,231)
Outstanding at end of year, shares	964,359	2,238,590
Vested/Exercisable at end of year, shares	964,359
Outstanding at beginning of year, Weighted Average Exercise Price	$ 15.67
Exercised, Weighted Average Exercise Price	0
Forfeited/Expired, Weighted Average Exercise Price	20.61
Outstanding at end of year, Weighted Average Exercise Price	9.13	$ 15.67
Vested/Exercisable at end of period, Weighted Average Exercise Price	$ 9.13
Weighted Average Remaining Contractual Term (in years)	1 year 3 months	1 year 1 month 6 days
Vested/Exercisable at end of period, Weighted Average Remaining Contractual Term (in years)	1 year 3 months
Exercised, Aggregated Intrinsic Value	$ 0
Outstanding at end of year, Aggregate Intrinsic Value	3,652,903
Vested/Exercisable at end of year, Aggregate Intrinsic Value	$ 3,652,903

Share Based Compensation, 401_5

Share Based Compensation, 401(k) Plan and Deferred Compensation - Restricted Share Activity (Details) - Restricted Share Rights Awards [Member]	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested at January 1, 2018, shares | shares	455,643
Granted, shares | shares	220,241
Vested, shares | shares	(197,344)
Forfeited, shares | shares	(12,101)
Non-vested at December 31, 2018, shares | shares	466,439
Non-vested at January 1, 2018, Weighted Average Grant Date Fair Value | $ / shares	$ 14.95
Granted, Weighted Average Grant Date Fair Value | $ / shares	15.71
Vested, Weighted Average Grant Date Fair Value | $ / shares	15.87
Forfeited, Weighted Average Grant Date Fair Value | $ / shares	15.04
Non-vested at December 31, 2018, Weighted Average Grant Date Fair Value | $ / shares	$ 14.93
Non-vested at January 1, 2018, Aggregate Intrinsic Value | $	$ 8,288,146
Granted, Aggregate Intrinsic Value | $	0
Vested, Aggregate Intrinsic Value | $	5,923
Forfeited, Aggregate Intrinsic Value | $	23,292
Non-vested at December 31, 2018, Aggregate Intrinsic Value | $	$ 70,677

Share Based Compensation, 401_6

Share Based Compensation, 401(k) Plan and Deferred Compensation - Restricted Performance Share Units (Details) - USD ($) $ in Thousands	Feb. 28, 2018	Mar. 01, 2017	Feb. 22, 2016	Dec. 31, 2018	May 18, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Units Granted					6,500,000
Restricted Performance Share Units Plan [Member] | Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested at January 1, 2018, shares				400,488
Granted, shares				209,193
Units Cancelled				(9,408)
Non-vested at December 31, 2018, shares				600,273
Units Granted	209,193	174,854	231,388
Fair Value of Units on Grant Date (in thousands)	$ 4,276	$ 3,735	$ 3,558
Restricted Performance Share Units Plan [Member] | February 22, 2016 RSPU Grant [Member] | Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested at January 1, 2018, shares				228,077
Granted, shares				0
Units Cancelled				(3,354)
Non-vested at December 31, 2018, shares				224,723
Measurement Period Commencement Date				Jan. 1, 2016
Measurement Period End Date				Dec. 31, 2018
Restricted Performance Share Units Plan [Member] | March 01, 2017 RSPU Grant [Member] | Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested at January 1, 2018, shares				172,411
Granted, shares				0
Units Cancelled				(2,886)
Non-vested at December 31, 2018, shares				169,525
Measurement Period Commencement Date				Jan. 1, 2017
Measurement Period End Date				Dec. 31, 2019
Restricted Performance Share Units Plan [Member] | February 28, 2018 RSPU Grant [Member] | Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested at January 1, 2018, shares				0
Granted, shares				209,193
Units Cancelled				(3,168)
Non-vested at December 31, 2018, shares				206,025
Measurement Period Commencement Date				Jan. 1, 2018
Measurement Period End Date				Dec. 31, 2020

Distributions - Tax Characteris

Distributions - Tax Characteristics of Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Distributions [Abstract]
Common Share Distributions Payments of Ordinary Dividends	$ 0.55	$ 0.38	$ 0
Common Share Distributions Capital Gain	0	0.26	0.62
Common Share Distributions Non-taxable Distributions	0.17	0	0
Common Stock, Dividends, Per Share, Paid	$ 0.72	$ 0.64	$ 0.62
Percentage Of Distributions classified as ordinary income	76.20%	60.00%	0.00%
Percentage Of Distributions classified as capital gain	0.00%	40.00%	100.00%
Percentage Of Distributions classified as non-taxable distribution	23.80%	0.00%	0.00%
Dividends, Preferred Stock	$ 0	$ 2,032	$ 6,900
Percentage Of Preferred Distributions classified as ordinary income	0.00%	60.00%	0.00%
Percentage Of Preferred Distributions classified as capital gain	0.00%	40.00%	100.00%
Percentage Of Preferred Distributions classified as non-taxable distribution	0.00%	0.00%	0.00%

Income Taxes and Tax Credit T_2

Income Taxes and Tax Credit Transactions (Textual) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Tax Credit Carryforward [Line Items]
Accruals for tax uncertainties	$ 0	$ 0
Deferred income tax benefit	300,000	(600,000)
Current Income Tax Expense (Benefit)	100,000
Other Assets [Member]
Tax Credit Carryforward [Line Items]
Net deferred tax assets	$ 100,000	$ 600,000

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1		$ 2,399
Amortization of interest rate contracts reclassified from comprehensive income to interest expense	[1]	1,191	$ 1,230	$ 1,104
Balance at December 31,		5,029	2,399
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1		2,056
Amortization of interest rate contracts reclassified from comprehensive income to interest expense	[2]	1,191	1,230	1,104
Balance at December 31,		4,725	2,056
Accumulated Other Comprehensive Income (Loss) [Member]
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1		2,399	(1,745)	(5,192)
Change in fair market value during year		1,478	2,948	2,371
Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests		(39)	(34)	(28)
Amortization of interest rate contracts reclassified from comprehensive income to interest expense		1,191	1,230	1,104
Balance at December 31,		5,029	2,399	(1,745)
Accumulated Other Comprehensive Income (Loss) [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1		2,056	(2,122)	(5,597)
Change in fair market value during year		1,478	2,948	2,371
Amortization of interest rate contracts reclassified from comprehensive income to interest expense		1,191	1,230	1,104
Balance at December 31,		$ 4,725	$ 2,056	$ (2,122)
[1]	Amounts reclassified from comprehensive income to interest expense within the Consolidated Statements of Operations.
[2]	Amounts reclassified from comprehensive income to interest expense within the Consolidated Statement of Operations.

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Loss) (Textual) (Details) $ in Millions	Dec. 31, 2018USD ($)
Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]
Gains (losses) expected to be reclassified from AOCI into interest expense within the next twelve months	$ 0.8

Segment Information (Textual) (

Segment Information (Textual) (Details)	12 Months Ended
	Dec. 31, 2018segment
Segment Reporting [Abstract]
Number of Reportable Segments	5

Segment Information - Real Esta

Segment Information - Real Estate Investments, at Cost of Company's Reportable Segments (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating properties		$ 3,953,319	$ 3,832,348	$ 3,586,295
Assets held for sale	[1]	0	0	73,591
Operating Properties		3,953,319	3,832,348	3,659,886
Construction-in-progress		150,263	121,188	297,462
Land held for development	[2]	86,401	98,242	150,970
Prepaid leasehold interests in land held for development, net	[3]	39,999	0	0
Philadelphia CBD [Member]
Segment Reporting Information [Line Items]
Operating properties		1,670,388	1,643,296	1,320,974
Pennsylvania Suburbs [Member]
Segment Reporting Information [Line Items]
Operating properties		1,004,537	958,796	1,005,446
Metropolitan DC [Member]
Segment Reporting Information [Line Items]
Operating properties	[4]	524,190	978,257	975,987
Austin, Texas [Member]
Segment Reporting Information [Line Items]
Operating properties	[5]	667,698	163,653	146,794
Other [Member]
Segment Reporting Information [Line Items]
Operating properties		$ 86,506	$ 88,346	$ 137,094
[1]	As of December 31, 2016, three office properties in the Metropolitan Washington, D.C. segment and two office properties in the Other segment were classified as held for sale in accordance with applicable accounting standards for long-lived assets. See the “ 2016 ” section of Note 3, “Real Estate Investments,” for further information.
[2]	As of December 31, 2018, the Company classified 37.9 acres of land held for development , comprised of 2.7 acres and 35.2 acres, located in its Pennsylvania Suburbs segment and Other segment, respectively, as held for sale in accordance with applicable accounting standards for long lived assets. See Note 3 , “Real Estate Investments,” for further information. As of December 31, 2017, the Company classified 13.1 acres of land held for development located in its Other segment as held for sale in accordance with applicable accounting standards for long lived assets.
[3]	As of December 31, 2018, this caption comprised leasehold interests in prepaid 99-year ground leases at 3025 and 3001-3003 JFK Boulevard, in Philadelphia, Pennsylvania. See Note 3, “Real Estate Investments
[4]	On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment, known as the Rockpoint Portfolio, to the Herndon Innovation Center Metro Portfolio Venture, LLC for a gross sales price of $312.0 million. The Company and its partner own 15% and 85% interests in the Herndon Innovation Center Metro Portfolio Venture, LLC, respectively. The Herndon Innovation Center Metro Portfolio Venture, LLC funded the acquisition with $265.2 million of cash, which was distributed to the Company at closing. After funding its share of closing costs and working capital contributions of $2.2 million and $0.6 million, respectively, the Company received $262.4 million of cash proceeds at settlement. For further information related to this transaction, see the “ Herndon Innovation Center Metro Portfolio Venture, LLC Investment in Unconsolidated Real Estate Ventures
[5]	On December 11, 2018, the Company acquired from DRA Advisors its 50% ownership interest in the G&I Austin Office LLC real estate venture for an aggregate purchase price of $535.1 million. The DRA Austin Venture owned twelve office properties containing an aggregate 1,570,123 square feet, located in Austin, Texas. As a result of the acquisition, the Company acquired complete ownership of the Austin Venture Portfolio. For further information related to this transaction, see the “ Acquisitions” Real Estate Investments

Segment Information - Real Es_2

Segment Information - Real Estate Investments, at Cost of Company's Reportable Segments (Parenthetical) (Details) $ in Thousands	Dec. 20, 2018USD ($)ft²property	Dec. 11, 2018USD ($)ft²property	Dec. 31, 2018USD ($)ft²aproperty	Dec. 31, 2017USD ($)a	Dec. 31, 2016USD ($)property	Mar. 31, 2017property	Dec. 31, 2016Office	Mar. 31, 2016property
Segment Reporting Information [Line Items]
Area of Real Estate Property | ft²			16,777,249
Proceeds from the sale of properties			$ 324,090	$ 171,860	$ 784,331
Number of Properties | property			97
Assets Held-for-sale [Member]
Segment Reporting Information [Line Items]
Acreage of land | a				13.1
Assets Held-for-sale [Member] | Land Held For Development [Member]
Segment Reporting Information [Line Items]
Acreage of land | a			37.9
Metropolitan DC [Member]
Segment Reporting Information [Line Items]
Number of Properties							3	2
Other [Member]
Segment Reporting Information [Line Items]
Number of Properties			1		3	4	2
Other [Member] | Assets Held-for-sale [Member] | Land Held For Development [Member]
Segment Reporting Information [Line Items]
Acreage of land | a			35.2	13.1
Pennsylvania Suburbs [Member] | Assets Held-for-sale [Member] | Land Held For Development [Member]
Segment Reporting Information [Line Items]
Acreage of land | a			2.7
DRA Austin Venture [Member]
Segment Reporting Information [Line Items]
Area of Real Estate Property | ft²		1,570,123
Ownership percentage		50.00%
Number of Properties | property		12
Aggregate purchase price		$ 535,100
3001-3003 and 3025 JFK Boulevard [Member]
Segment Reporting Information [Line Items]
Lease agreement term			99 years
Herndon Innovation Center Metro Portfolio Venture, LLC [Member] | Metropolitan Washington, D.C. - Office [Member]
Segment Reporting Information [Line Items]
Number of properties contributed to a joint venture | property	8
Area of Real Estate Property | ft²	1,293,197
Aggregate gross sales price of a joint venture	$ 312,000
Ownership percentage	15.00%
Cash proceeds received from sale of properties	$ 265,200
Closing costs	2,200
Working capital contribution	600
Proceeds from the sale of properties	$ 262,400
Herndon Innovation Center Metro Portfolio Venture, LLC [Member] | Metropolitan Washington, D.C. - Office [Member] | Rockpoint [Member]
Segment Reporting Information [Line Items]
Ownership percentage	85.00%

Segment Information - Net Opera

Segment Information - Net Operating Income of Company's Reportable Segments (Details) - USD ($) $ in Thousands		3 Months Ended									12 Months Ended
		Dec. 31, 2018	[1]	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total revenue		$ 139,203		$ 134,998	$ 133,786	$ 136,358	$ 133,344	$ 128,438	$ 127,791	$ 130,920	$ 544,345		$ 520,493	$ 525,463
Operating expenses	[2]										(218,023)		(205,999)	(209,448)
Net operating income (loss)											326,322		314,494	316,015
Philadelphia CBD [Member]
Segment Reporting Information [Line Items]
Total revenue											256,717
Pennsylvania Suburbs [Member]
Segment Reporting Information [Line Items]
Total revenue											138,279
Metropolitan DC [Member]
Segment Reporting Information [Line Items]
Total revenue											90,308
Austin, Texas [Member]
Segment Reporting Information [Line Items]
Total revenue											38,665
Other [Member]
Segment Reporting Information [Line Items]
Total revenue											16,757
Operating Segments [Member] | Philadelphia CBD [Member]
Segment Reporting Information [Line Items]
Total revenue											256,717		226,673	200,245
Operating expenses	[2]										(99,449)		(88,818)	(78,708)
Net operating income (loss)											157,268		137,855	121,537
Operating Segments [Member] | Pennsylvania Suburbs [Member]
Segment Reporting Information [Line Items]
Total revenue											138,279		139,785	144,338
Operating expenses	[2]										(49,357)		(47,769)	(49,208)
Net operating income (loss)											88,922		92,016	95,130
Operating Segments [Member] | Metropolitan DC [Member]
Segment Reporting Information [Line Items]
Total revenue											90,308		92,024	99,781
Operating expenses	[2]										(34,072)		(35,014)	(39,036)
Net operating income (loss)											56,236		57,010	60,745
Operating Segments [Member] | Austin, Texas [Member]
Segment Reporting Information [Line Items]
Total revenue											38,665		34,301	34,585
Operating expenses	[2]										(16,739)		(15,456)	(13,222)
Net operating income (loss)											21,926		18,845	21,363
Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Total revenue											16,757		18,347	39,359
Operating expenses	[2]										(11,888)		(11,749)	(23,204)
Net operating income (loss)											4,869		6,598	16,155
Corporate [Member]
Segment Reporting Information [Line Items]
Total revenue											3,619	[3]	9,363	7,155
Operating expenses	[2]										(6,518)		(7,193)	(6,070)
Net operating income (loss)											$ (2,899)		$ 2,170	$ 1,085
[1]	The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, “Real Estate Investments,” for further information on this transaction.
[2]	Includes property operating expense, real estate taxes and third party management expense.
[3]	Corporate includes intercompany eliminations necessary to reconcile to consolidated Company totals.

Segment Information - Unconsoli

Segment Information - Unconsolidated Real Estate Ventures of Company's Reportable Segments (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Investment in real estate ventures, at equity		$ 169,100	$ 194,621	$ 281,331
Equity in loss of Real Estate Ventures		(15,231)	(8,306)	(11,503)
Philadelphia CBD [Member]
Segment Reporting Information [Line Items]
Investment in real estate ventures, at equity		19,897	39,939	48,691
Equity in loss of Real Estate Ventures		(105)	255	(686)
Pennsylvania Suburbs [Member]
Segment Reporting Information [Line Items]
Investment in real estate ventures, at equity		0	3,503	15,421
Equity in loss of Real Estate Ventures		0	631	748
Metropolitan DC [Member]
Segment Reporting Information [Line Items]
Investment in real estate ventures, at equity	[1]	136,142	119,817	141,786
Equity in loss of Real Estate Ventures	[1]	(15,065)	(5,044)	(6,293)
MAP Venture [Member]
Segment Reporting Information [Line Items]
Investment in real estate ventures, at equity	[2]	11,173	15,450	20,893
Equity in loss of Real Estate Ventures	[2]	(2,155)	(3,443)	(4,218)
Other [Member]
Segment Reporting Information [Line Items]
Investment in real estate ventures, at equity		1,888	1,939	1,654
Equity in loss of Real Estate Ventures		407	285	814
Austin, Texas [Member]
Segment Reporting Information [Line Items]
Investment in real estate ventures, at equity	[3]	0	13,973	52,886
Equity in loss of Real Estate Ventures	[3]	$ 1,687	$ (990)	$ (1,868)
[1]	On December 20, 2018, the Company formed a joint venture with Rockpoint. See footnote (a) to the “Real estate investments, at cost”
[2]	The MAP Venture represents a joint venture formed between the Company and MAP Ground Lease Holdings LLC, an affiliate of Och-Ziff Capital Management Group, LLC, on February 4, 2016. The MAP Venture’s business operations, including properties in Richmond, Virginia; Metropolitan Washington, D.C.; New Jersey/Delaware and Pennsylvania Suburbs, are centrally managed with the results reported to management of the Company on a consolidated basis. As a result, the investment in the MAP Venture is separately presented. All other unconsolidated real estate ventures are managed consistently with the Company’s regional segments.
[3]	See footnote (b) to the “Real estate investments, at cost” table above for further information regarding this transaction.

Segment Information - Reconcili

Segment Information - Reconciliation of Consolidated Net Income (Loss) to Consolidated NOI (Details) - USD ($) $ in Thousands	3 Months Ended											12 Months Ended
	Dec. 31, 2018	[1]	Sep. 30, 2018	[2]	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting [Abstract]
Net income	$ 122,710		$ (43,262)		$ 13,136	$ 44,705	$ 73,844	$ 19,046	$ 7,698	$ 21,271		$ 137,289	$ 121,859	$ 40,501
Plus:
Interest expense												78,199	81,886	84,708
Interest expense - amortization of deferred financing costs												2,498	2,435	2,696
Interest expense - financing obligation												0	0	679
Depreciation and amortization												174,259	179,357	189,676
General and administrative expenses												27,802	28,538	26,596
Equity in loss of Real Estate Ventures												15,231	8,306	11,503
Provision for impairment											$ 1,800	71,707	3,057	40,517
Loss on early extinguishment of debt												105	3,933	66,590
Less:
Interest income												4,703	1,113	1,236
Income tax (provision) benefit												(423)	628	0
Net gain on disposition of real estate												2,932	31,657	116,983
Net gain on sale of undepreciated real estate												3,040	953	9,232
Net gain on real estate venture transactions												142,233	80,526	20,000
Gain on promoted interest in unconsolidated real estate venture												28,283	0	0
Consolidated net operating income												$ 326,322	$ 314,494	$ 316,015
[1]	The increase in net income for the fourth quarter primarily relates to gains of $103.8 million and $28.3 million, recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, "Real Estate Investments."
[2]	The decrease in third quarter net income primarily relates to a $56.9 million impairment charge which related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, “Real Estate Investments,”

Operating Leases - Additional I

Operating Leases - Additional Information (Details)	12 Months Ended
	Dec. 31, 2018
Leases Operating [Abstract]
Lessor, operating lease, description	The Company leases properties to tenants under operating leases with various expiration dates extending to 2082.
Operating lease extending expiration date	2,082

Operating Leases - Minimum Futu

Operating Leases - Minimum Future Rentals on Non-cancelable Leases of Company properties leased to Tenants (Details) $ in Thousands	Dec. 31, 2018USD ($)
Operating Leases, Future Minimum Payments Receivable [Abstract]
2,019	$ 392,058
2,020	372,619
2,021	349,160
2,022	304,445
2,023	277,388
Thereafter	$ 1,265,810

Commitments and Contingencies_2

Commitments and Contingencies (Textual) (Details)	Apr. 02, 2015USD ($)	Sep. 30, 2004USD ($)	Dec. 31, 2018USD ($)ft²	Dec. 31, 2017USD ($)	Oct. 13, 2017USD ($)
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness			$ 370,319,000	$ 768,912,000
Loan outstanding principal balance			$ 2,028,046,000	1,930,828,000
Agreed holding period (not to sell) for properties acquired as part of the TRC acquisition			15 years
4040 Wilson Venture [Member]
Property Subject to or Available for Operating Lease [Line Items]
Guarantees, maximum exposure amount			$ 41,300,000
Loan outstanding principal balance			$ 150,000,000
Prentiss Properties Trust [Member] | Commerce Square [Member]
Property Subject to or Available for Operating Lease [Line Items]
Non-controlling interest, ownership percentage by non-controlling Owners			1.00%
Unconsolidated Real Estate Ventures [Member]
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness			$ 370,319,000
PJP VII [Member]
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness			3,777,000	$ 4,792,000
Guarantees, maximum exposure amount			300,000
Loan outstanding principal balance			3,800,000
618 Market Street [Member]
Property Subject to or Available for Operating Lease [Line Items]
Contingent consideration, liability	$ 2,000,000		1,900,000
Fair value of contingent consideration	1,600,000
Interest expense	$ 2,000,000
The Bulletin Building [Member]
Property Subject to or Available for Operating Lease [Line Items]
Funding requirement met for capital improvements			1,200,000
Estimated of funding In the ground lease			37,300,000
Estimated aggregate cost			83,100,000
Acquisition cost, inclusive in estimated aggregate cost					$ 37,800,000
Drexel Square [Member]
Property Subject to or Available for Operating Lease [Line Items]
Required spending in capital improvements to property			2,700,000
Estimated potential additional contribution obligation			$ 600,000
Two Logan Square [Member]
Property Subject to or Available for Operating Lease [Line Items]
Leased Area Of Building | ft²			708,844
Amount to be paid if the Company takes fee title to Two Logan Square upon foreclosure of related mortgage			$ 2,900,000
Liability related to acquisition of TRC		$ 700,000	2,700,000
One Commerce Square [Member]
Property Subject to or Available for Operating Lease [Line Items]
Tax guarantee obligation			125,000,000
Two Commerce Square [Member]
Property Subject to or Available for Operating Lease [Line Items]
Tax guarantee obligation			$ 100,000,000
Minimum [Member]
Property Subject to or Available for Operating Lease [Line Items]
Lease terms			10 years
Minimum [Member] | The Bulletin Building [Member]
Property Subject to or Available for Operating Lease [Line Items]
Required spending in capital improvements to property			$ 8,000,000
Maximum [Member]
Property Subject to or Available for Operating Lease [Line Items]
Lease terms			66 years
Mortgage Lenders [Member]
Property Subject to or Available for Operating Lease [Line Items]
Associated letter of credit			$ 0

Commitments and Contingencies -

Commitments and Contingencies - Minimum Future Rental Payments on Non-cancelable Leases (Details) $ in Thousands	Dec. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,019	$ 1,222
2,020	1,222
2,021	1,222
2,022	1,222
2,023	1,222
Thereafter	55,689
Total	$ 61,799

Subsequent Events (Textual) (De

Subsequent Events (Textual) (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 03, 2019
Subsequent Event [Line Items]
Repurchased and Retired, Shares		1,729,278	0	0
Share Price		$ 12.64
Repurchased and Retired, Value		$ 21,858,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Authorized Amount					$ 150,000,000
Repurchased and Retired, Shares	1,337,169
Share Price	$ 12.92
Repurchased and Retired, Value	$ 17,300,000

Summary of Quarterly Results (D

Summary of Quarterly Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information [Line Items]
Total revenue	$ 139,203	[1]	$ 134,998		$ 133,786	$ 136,358	$ 133,344	$ 128,438	$ 127,791	$ 130,920	$ 544,345	$ 520,493	$ 525,463
Net income (loss)	122,710	[2]	(43,262)	[3]	13,136	44,705	73,844	19,046	7,698	21,271	137,289	121,859	40,501
Net income (loss) allocated to Common Shares/ Partnership Unitholders	$ 121,823		$ (43,003)		$ 12,920	$ 44,215	$ 73,137	$ 18,803	$ 4,092	$ 19,278	$ 136,324	$ 120,850	$ 40,191
Basic earnings (loss) per Common Shares/Partnership Unitholders	$ 0.68		$ (0.24)		$ 0.07	$ 0.25	$ 0.42	$ 0.11	$ 0.02	$ 0.11	$ 0.76	$ 0.66	$ 0.19
Diluted earnings (loss) per Common Share/ Partnership Unitholders	$ 0.68		$ (0.24)		$ 0.07	$ 0.25	$ 0.41	$ 0.11	$ 0.02	$ 0.11	$ 0.76	$ 0.65	$ 0.19
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Quarterly Financial Information [Line Items]
Total revenue	$ 139,203	[1]	$ 134,998		$ 133,786	$ 136,358	$ 133,344	$ 128,438	$ 127,791	$ 130,920	$ 544,345	$ 520,493	$ 525,463
Net income (loss)	122,710	[2]	(43,262)	[3]	13,136	44,705	73,844	19,046	7,698	21,271	$ 137,289	$ 121,859	$ 40,501
Net income (loss) allocated to Common Shares/ Partnership Unitholders	$ 122,612		$ (43,362)		$ 13,029	$ 44,586	$ 73,758	$ 18,961	$ 4,129	$ 19,442
Basic earnings (loss) per Common Shares/Partnership Unitholders	$ 0.68		$ (0.24)		$ 0.07	$ 0.25	$ 0.42	$ 0.11	$ 0.02	$ 0.11	$ 0.76	$ 0.66	$ 0.19
Diluted earnings (loss) per Common Share/ Partnership Unitholders	$ 0.68		$ (0.24)		$ 0.07	$ 0.25	$ 0.41	$ 0.11	$ 0.02	$ 0.11	$ 0.76	$ 0.65	$ 0.19
[1]	The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, “Real Estate Investments,” for further information on this transaction.
[2]	The increase in net income for the fourth quarter primarily relates to gains of $103.8 million and $28.3 million, recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, "Real Estate Investments."
[3]	The decrease in third quarter net income primarily relates to a $56.9 million impairment charge which related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, “Real Estate Investments,”

Summary of Quarterly Results (P

Summary of Quarterly Results (Parenthetical) (Details) $ in Thousands	Dec. 11, 2018USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)property	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions				$ 142,233	$ 80,526	$ 20,000
Gain on promoted interest in unconsolidated real estate venture				28,283	0	0
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions				142,233	80,526	20,000
Gain on promoted interest in unconsolidated real estate venture				$ 28,283	$ 0	$ 0
DRA Austin Venture [Member]
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions	$ 103,800	$ 103,800
Gain on promoted interest in unconsolidated real estate venture	$ 28,300	28,300
DRA Austin Venture [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions		103,800
Gain on promoted interest in unconsolidated real estate venture		$ 28,300
Metropolitan Washington, D.C. - Office [Member]
Quarterly Financial Information [Line Items]
Provision for impairment on assets held for sale			$ 56,900
Number of properties contributed to a joint venture | property			8
Metropolitan Washington, D.C. - Office [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Quarterly Financial Information [Line Items]
Provision for impairment on assets held for sale			$ 56,900
Number of properties contributed to a joint venture | property			8

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Balance at Beginning of Period	$ 17,112	$ 16,116	$ 16,178
Valuation Allowances and Reserves, Additions	1,775	1,912	2,207
Valuation Allowances and Reserves, Deductions	5,968	916	2,269
Valuation Allowances and Reserves, Balance at End of Period	$ 12,919	$ 17,112	$ 16,116

Schedule III - Real Estate an_2

Schedule III - Real Estate and Accumulated Depreciation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 323,032,000
Initial Cost [Abstract]
Land	453,723,000
Buildings and Improvements	2,863,832,000
Net Improvements (Retirements) Since Acquisition	635,764,000
Carrying Amount at Which Carried [Abstract]
Land	508,363,000
Buildings and Improvements	3,444,955,000
Total	3,953,319,000	$ 3,832,348,000	$ 3,659,886,000	$ 4,487,588,000
Accumulated Depreciation at December 31, 2018	865,462,000	$ 895,091,000	$ 885,392,000	$ 1,080,616,000
PENNSYLVANIA SUBURBS [Member] | 400 Berwyn Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	2,657,000
Buildings and Improvements	4,462,000
Net Improvements (Retirements) Since Acquisition	12,985,000
Carrying Amount at Which Carried [Abstract]
Land	2,657,000
Buildings and Improvements	17,447,000
Total	20,104,000
Accumulated Depreciation at December 31, 2018	$ 8,060,000
Real Estate And Accumulated Depreciation Construction Year	1,999
Real Estate And Accumulated Depreciation Year Of Acquisition	1,999
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 300 Berwyn Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,206,000
Buildings and Improvements	13,422,000
Net Improvements (Retirements) Since Acquisition	3,331,000
Carrying Amount at Which Carried [Abstract]
Land	2,206,000
Buildings and Improvements	16,753,000
Total	18,959,000
Accumulated Depreciation at December 31, 2018	$ 9,777,000
Real Estate And Accumulated Depreciation Construction Year	1,989
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 1050 Westlakes Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,611,000
Buildings and Improvements	10,445,000
Net Improvements (Retirements) Since Acquisition	2,416,000
Carrying Amount at Which Carried [Abstract]
Land	2,611,000
Buildings and Improvements	12,861,000
Total	15,472,000
Accumulated Depreciation at December 31, 2018	$ 5,990,000
Real Estate And Accumulated Depreciation Construction Year	1,984
Real Estate And Accumulated Depreciation Year Of Acquisition	1,999
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 1200 Swedesford Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,595,000
Buildings and Improvements	11,809,000
Net Improvements (Retirements) Since Acquisition	218,000
Carrying Amount at Which Carried [Abstract]
Land	2,595,000
Buildings and Improvements	12,027,000
Total	14,622,000
Accumulated Depreciation at December 31, 2018	$ 6,211,000
Real Estate And Accumulated Depreciation Construction Year	1,994
Real Estate And Accumulated Depreciation Year Of Acquisition	2,001
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 200 Berwyn Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,533,000
Buildings and Improvements	9,460,000
Net Improvements (Retirements) Since Acquisition	2,074,000
Carrying Amount at Which Carried [Abstract]
Land	1,533,000
Buildings and Improvements	11,534,000
Total	13,067,000
Accumulated Depreciation at December 31, 2018	$ 6,586,000
Real Estate And Accumulated Depreciation Construction Year	1,987
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 1180 Swedesford Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,086,000
Buildings and Improvements	8,342,000
Net Improvements (Retirements) Since Acquisition	3,110,000
Carrying Amount at Which Carried [Abstract]
Land	2,086,000
Buildings and Improvements	11,452,000
Total	13,538,000
Accumulated Depreciation at December 31, 2018	$ 5,496,000
Real Estate And Accumulated Depreciation Construction Year	1,987
Real Estate And Accumulated Depreciation Year Of Acquisition	2,001
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 100 Berwyn Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,180,000
Buildings and Improvements	7,290,000
Net Improvements (Retirements) Since Acquisition	1,636,000
Carrying Amount at Which Carried [Abstract]
Land	1,180,000
Buildings and Improvements	8,926,000
Total	10,106,000
Accumulated Depreciation at December 31, 2018	$ 5,012,000
Real Estate And Accumulated Depreciation Construction Year	1,986
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 1160 Swedesford Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,781,000
Buildings and Improvements	7,124,000
Net Improvements (Retirements) Since Acquisition	6,831,000
Carrying Amount at Which Carried [Abstract]
Land	2,045,000
Buildings and Improvements	13,691,000
Total	15,736,000
Accumulated Depreciation at December 31, 2018	$ 5,864,000
Real Estate And Accumulated Depreciation Construction Year	1,986
Real Estate And Accumulated Depreciation Year Of Acquisition	2,001
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 1100 Cassett Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,695,000
Buildings and Improvements	6,779,000
Net Improvements (Retirements) Since Acquisition	1,662,000
Carrying Amount at Which Carried [Abstract]
Land	1,695,000
Buildings and Improvements	8,441,000
Total	10,136,000
Accumulated Depreciation at December 31, 2018	$ 3,714,000
Real Estate And Accumulated Depreciation Construction Year	1,997
Real Estate And Accumulated Depreciation Year Of Acquisition	2,001
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | Six Tower Bridge (181 Washington Street) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	6,927,000
Buildings and Improvements	14,722,000
Net Improvements (Retirements) Since Acquisition	2,448,000
Carrying Amount at Which Carried [Abstract]
Land	6,237,000
Buildings and Improvements	17,860,000
Total	24,097,000
Accumulated Depreciation at December 31, 2018	$ 2,920,000
Real Estate And Accumulated Depreciation Construction Year	1,999
Real Estate And Accumulated Depreciation Year Of Acquisition	2,013
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 52 Swedesford Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	4,241,000
Buildings and Improvements	16,579,000
Net Improvements (Retirements) Since Acquisition	5,418,000
Carrying Amount at Which Carried [Abstract]
Land	4,241,000
Buildings and Improvements	21,997,000
Total	26,238,000
Accumulated Depreciation at December 31, 2018	$ 10,712,000
Real Estate And Accumulated Depreciation Construction Year	1,988
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 640 Freedom Business Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	4,222,000
Buildings and Improvements	16,891,000
Net Improvements (Retirements) Since Acquisition	4,827,000
Carrying Amount at Which Carried [Abstract]
Land	4,222,000
Buildings and Improvements	21,718,000
Total	25,940,000
Accumulated Depreciation at December 31, 2018	$ 11,254,000
Real Estate And Accumulated Depreciation Construction Year	1,991
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 620 Freedom Business Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,770,000
Buildings and Improvements	11,014,000
Net Improvements (Retirements) Since Acquisition	2,147,000
Carrying Amount at Which Carried [Abstract]
Land	2,770,000
Buildings and Improvements	13,161,000
Total	15,931,000
Accumulated Depreciation at December 31, 2018	$ 6,925,000
Real Estate And Accumulated Depreciation Construction Year	1,986
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 1000 First Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,772,000
Buildings and Improvements	10,936,000
Net Improvements (Retirements) Since Acquisition	3,660,000
Carrying Amount at Which Carried [Abstract]
Land	2,772,000
Buildings and Improvements	14,596,000
Total	17,368,000
Accumulated Depreciation at December 31, 2018	$ 7,255,000
Real Estate And Accumulated Depreciation Construction Year	1,980
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 630 Freedom Business Center Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,773,000
Buildings and Improvements	11,144,000
Net Improvements (Retirements) Since Acquisition	3,592,000
Carrying Amount at Which Carried [Abstract]
Land	2,773,000
Buildings and Improvements	14,736,000
Total	17,509,000
Accumulated Depreciation at December 31, 2018	$ 7,517,000
Real Estate And Accumulated Depreciation Construction Year	1,989
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 1060 First Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,712,000
Buildings and Improvements	10,953,000
Net Improvements (Retirements) Since Acquisition	3,539,000
Carrying Amount at Which Carried [Abstract]
Land	2,712,000
Buildings and Improvements	14,492,000
Total	17,204,000
Accumulated Depreciation at December 31, 2018	$ 7,111,000
Real Estate And Accumulated Depreciation Construction Year	1,987
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 1020 First Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,168,000
Buildings and Improvements	8,576,000
Net Improvements (Retirements) Since Acquisition	3,939,000
Carrying Amount at Which Carried [Abstract]
Land	2,168,000
Buildings and Improvements	12,515,000
Total	14,683,000
Accumulated Depreciation at December 31, 2018	$ 6,004,000
Real Estate And Accumulated Depreciation Construction Year	1,984
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 610 Freedom Business Center Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,017,000
Buildings and Improvements	8,070,000
Net Improvements (Retirements) Since Acquisition	2,547,000
Carrying Amount at Which Carried [Abstract]
Land	2,017,000
Buildings and Improvements	10,617,000
Total	12,634,000
Accumulated Depreciation at December 31, 2018	$ 5,319,000
Real Estate And Accumulated Depreciation Construction Year	1,985
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 1040 First Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,860,000
Buildings and Improvements	11,282,000
Net Improvements (Retirements) Since Acquisition	5,037,000
Carrying Amount at Which Carried [Abstract]
Land	2,860,000
Buildings and Improvements	16,319,000
Total	19,179,000
Accumulated Depreciation at December 31, 2018	$ 7,941,000
Real Estate And Accumulated Depreciation Construction Year	1,985
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 650 Park Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,916,000
Buildings and Improvements	4,378,000
Net Improvements (Retirements) Since Acquisition	1,357,000
Carrying Amount at Which Carried [Abstract]
Land	1,916,000
Buildings and Improvements	5,735,000
Total	7,651,000
Accumulated Depreciation at December 31, 2018	$ 3,418,000
Real Estate And Accumulated Depreciation Construction Year	1,968
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 600 Park Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,012,000
Buildings and Improvements	4,048,000
Net Improvements (Retirements) Since Acquisition	385,000
Carrying Amount at Which Carried [Abstract]
Land	1,012,000
Buildings and Improvements	4,433,000
Total	5,445,000
Accumulated Depreciation at December 31, 2018	$ 2,527,000
Real Estate And Accumulated Depreciation Construction Year	1,964
Real Estate And Accumulated Depreciation Year Of Acquisition	1,998
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 933 First Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,127,000
Buildings and Improvements	20,794,000
Net Improvements (Retirements) Since Acquisition	(1,125,000)
Carrying Amount at Which Carried [Abstract]
Land	3,127,000
Buildings and Improvements	19,669,000
Total	22,796,000
Accumulated Depreciation at December 31, 2018	$ 1,345,000
Real Estate And Accumulated Depreciation Construction Year	2,017
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 500 North Gulph Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,303,000
Buildings and Improvements	5,201,000
Net Improvements (Retirements) Since Acquisition	18,777,000
Carrying Amount at Which Carried [Abstract]
Land	1,303,000
Buildings and Improvements	23,978,000
Total	25,281,000
Accumulated Depreciation at December 31, 2018	$ 82,000
Real Estate And Accumulated Depreciation Construction Year	1,979
Real Estate And Accumulated Depreciation Year Of Acquisition	1,996
PENNSYLVANIA SUBURBS [Member] | 401 Plymouth Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	6,199,000
Buildings and Improvements	16,131,000
Net Improvements (Retirements) Since Acquisition	16,184,000
Carrying Amount at Which Carried [Abstract]
Land	6,199,000
Buildings and Improvements	32,315,000
Total	38,514,000
Accumulated Depreciation at December 31, 2018	$ 14,477,000
Real Estate And Accumulated Depreciation Construction Year	2,001
Real Estate And Accumulated Depreciation Year Of Acquisition	2,000
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | Metroplex (4000 Chemical Road) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	4,373,000
Buildings and Improvements	24,546,000
Net Improvements (Retirements) Since Acquisition	452,000
Carrying Amount at Which Carried [Abstract]
Land	4,373,000
Buildings and Improvements	24,998,000
Total	29,371,000
Accumulated Depreciation at December 31, 2018	$ 6,941,000
Real Estate And Accumulated Depreciation Construction Year	2,007
Real Estate And Accumulated Depreciation Year Of Acquisition	2,001
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 610 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,651,000
Buildings and Improvements	14,514,000
Net Improvements (Retirements) Since Acquisition	3,313,000
Carrying Amount at Which Carried [Abstract]
Land	3,651,000
Buildings and Improvements	17,827,000
Total	21,478,000
Accumulated Depreciation at December 31, 2018	$ 7,996,000
Real Estate And Accumulated Depreciation Construction Year	1,987
Real Estate And Accumulated Depreciation Year Of Acquisition	2,002
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 600 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,652,000
Buildings and Improvements	15,288,000
Net Improvements (Retirements) Since Acquisition	2,377,000
Carrying Amount at Which Carried [Abstract]
Land	3,652,000
Buildings and Improvements	17,665,000
Total	21,317,000
Accumulated Depreciation at December 31, 2018	$ 7,422,000
Real Estate And Accumulated Depreciation Construction Year	1,986
Real Estate And Accumulated Depreciation Year Of Acquisition	2,002
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 630 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,558,000
Buildings and Improvements	14,743,000
Net Improvements (Retirements) Since Acquisition	2,522,000
Carrying Amount at Which Carried [Abstract]
Land	3,558,000
Buildings and Improvements	17,265,000
Total	20,823,000
Accumulated Depreciation at December 31, 2018	$ 7,157,000
Real Estate And Accumulated Depreciation Construction Year	1,988
Real Estate And Accumulated Depreciation Year Of Acquisition	2,002
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 620 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,572,000
Buildings and Improvements	14,435,000
Net Improvements (Retirements) Since Acquisition	1,561,000
Carrying Amount at Which Carried [Abstract]
Land	3,572,000
Buildings and Improvements	15,996,000
Total	19,568,000
Accumulated Depreciation at December 31, 2018	$ 6,517,000
Real Estate And Accumulated Depreciation Construction Year	1,990
Real Estate And Accumulated Depreciation Year Of Acquisition	2,002
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 660 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,694,000
Buildings and Improvements	5,487,000
Net Improvements (Retirements) Since Acquisition	20,715,000
Carrying Amount at Which Carried [Abstract]
Land	5,405,000
Buildings and Improvements	24,491,000
Total	29,896,000
Accumulated Depreciation at December 31, 2018	$ 5,636,000
Real Estate And Accumulated Depreciation Construction Year	1,987
Real Estate And Accumulated Depreciation Year Of Acquisition	2,012
Depreciable Life (Years)	30 years
PENNSYLVANIA SUBURBS [Member] | 351 Plymouth Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,043,000
Buildings and Improvements	555,000
Net Improvements (Retirements) Since Acquisition	0
Carrying Amount at Which Carried [Abstract]
Land	1,043,000
Buildings and Improvements	555,000
Total	1,598,000
Accumulated Depreciation at December 31, 2018	$ 191,000
Real Estate And Accumulated Depreciation Year Of Acquisition	2,000
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 150 Radnor Chester Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	11,925,000
Buildings and Improvements	36,986,000
Net Improvements (Retirements) Since Acquisition	9,273,000
Carrying Amount at Which Carried [Abstract]
Land	11,897,000
Buildings and Improvements	46,287,000
Total	58,184,000
Accumulated Depreciation at December 31, 2018	$ 20,332,000
Real Estate And Accumulated Depreciation Construction Year	1,983
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	29 years
PENNSYLVANIA SUBURBS [Member] | One Radnor Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	7,323,000
Buildings and Improvements	28,613,000
Net Improvements (Retirements) Since Acquisition	23,155,000
Carrying Amount at Which Carried [Abstract]
Land	7,323,000
Buildings and Improvements	51,768,000
Total	59,091,000
Accumulated Depreciation at December 31, 2018	$ 28,913,000
Real Estate And Accumulated Depreciation Construction Year	1,998
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	29 years
PENNSYLVANIA SUBURBS [Member] | 201 King of Prussia Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	8,956,000
Buildings and Improvements	29,811,000
Net Improvements (Retirements) Since Acquisition	3,064,000
Carrying Amount at Which Carried [Abstract]
Land	8,949,000
Buildings and Improvements	32,882,000
Total	41,831,000
Accumulated Depreciation at December 31, 2018	$ 18,605,000
Real Estate And Accumulated Depreciation Construction Year	2,001
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	25 years
PENNSYLVANIA SUBURBS [Member] | 555 Lancaster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	8,014,000
Buildings and Improvements	16,508,000
Net Improvements (Retirements) Since Acquisition	19,201,000
Carrying Amount at Which Carried [Abstract]
Land	8,609,000
Buildings and Improvements	35,114,000
Total	43,723,000
Accumulated Depreciation at December 31, 2018	$ 16,532,000
Real Estate And Accumulated Depreciation Construction Year	1,973
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	24 years
PENNSYLVANIA SUBURBS [Member] | Four Radnor Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	5,406,000
Buildings and Improvements	21,390,000
Net Improvements (Retirements) Since Acquisition	12,918,000
Carrying Amount at Which Carried [Abstract]
Land	5,705,000
Buildings and Improvements	34,009,000
Total	39,714,000
Accumulated Depreciation at December 31, 2018	$ 14,908,000
Real Estate And Accumulated Depreciation Construction Year	1,995
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	30 years
PENNSYLVANIA SUBURBS [Member] | Five Radnor Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	6,506,000
Buildings and Improvements	25,525,000
Net Improvements (Retirements) Since Acquisition	5,887,000
Carrying Amount at Which Carried [Abstract]
Land	6,578,000
Buildings and Improvements	31,340,000
Total	37,918,000
Accumulated Depreciation at December 31, 2018	$ 11,579,000
Real Estate And Accumulated Depreciation Construction Year	1,998
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	38 years
PENNSYLVANIA SUBURBS [Member] | Three Radnor Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	4,773,000
Buildings and Improvements	17,961,000
Net Improvements (Retirements) Since Acquisition	1,372,000
Carrying Amount at Which Carried [Abstract]
Land	4,791,000
Buildings and Improvements	19,315,000
Total	24,106,000
Accumulated Depreciation at December 31, 2018	$ 9,731,000
Real Estate And Accumulated Depreciation Construction Year	1,998
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	29 years
PENNSYLVANIA SUBURBS [Member] | Two Radnor Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,937,000
Buildings and Improvements	15,484,000
Net Improvements (Retirements) Since Acquisition	3,402,000
Carrying Amount at Which Carried [Abstract]
Land	3,942,000
Buildings and Improvements	18,881,000
Total	22,823,000
Accumulated Depreciation at December 31, 2018	$ 9,359,000
Real Estate And Accumulated Depreciation Construction Year	1,998
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	29 years
PENNSYLVANIA SUBURBS [Member] | 130 Radnor Chester Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,573,000
Buildings and Improvements	8,338,000
Net Improvements (Retirements) Since Acquisition	3,188,000
Carrying Amount at Which Carried [Abstract]
Land	2,567,000
Buildings and Improvements	11,532,000
Total	14,099,000
Accumulated Depreciation at December 31, 2018	$ 6,206,000
Real Estate And Accumulated Depreciation Construction Year	1,983
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	25 years
PENNSYLVANIA SUBURBS [Member] | Four Tower Bridge (200 Barr Harbor Drive)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 9,526,000
Initial Cost [Abstract]
Land	6,000,000
Buildings and Improvements	14,734,000
Net Improvements (Retirements) Since Acquisition	19,000
Carrying Amount at Which Carried [Abstract]
Land	6,000,000
Buildings and Improvements	14,753,000
Total	20,753,000
Accumulated Depreciation at December 31, 2018	$ 369,000
Real Estate And Accumulated Depreciation Construction Year	1,998
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 170 Radnor Chester Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,514,000
Buildings and Improvements	8,147,000
Net Improvements (Retirements) Since Acquisition	2,165,000
Carrying Amount at Which Carried [Abstract]
Land	2,509,000
Buildings and Improvements	10,317,000
Total	12,826,000
Accumulated Depreciation at December 31, 2018	$ 4,210,000
Real Estate And Accumulated Depreciation Construction Year	1,983
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	25 years
PENNSYLVANIA SUBURBS [Member] | 200 N. Radnor Chester Rd. [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,366,000
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	3,572,000
Carrying Amount at Which Carried [Abstract]
Land	3,366,000
Buildings and Improvements	3,572,000
Total	6,938,000
Accumulated Depreciation at December 31, 2018	$ 636,000
Real Estate And Accumulated Depreciation Construction Year	2,014
Real Estate And Accumulated Depreciation Year Of Acquisition	2,005
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 101 West Elm Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	6,251,000
Buildings and Improvements	25,209,000
Net Improvements (Retirements) Since Acquisition	3,633,000
Carrying Amount at Which Carried [Abstract]
Land	6,251,000
Buildings and Improvements	28,842,000
Total	35,093,000
Accumulated Depreciation at December 31, 2018	$ 9,723,000
Real Estate And Accumulated Depreciation Construction Year	1,999
Real Estate And Accumulated Depreciation Year Of Acquisition	2,005
Depreciable Life (Years)	40 years
PENNSYLVANIA SUBURBS [Member] | 1 West Elm Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,557,000
Buildings and Improvements	14,249,000
Net Improvements (Retirements) Since Acquisition	3,372,000
Carrying Amount at Which Carried [Abstract]
Land	3,557,000
Buildings and Improvements	17,621,000
Total	21,178,000
Accumulated Depreciation at December 31, 2018	$ 5,673,000
Real Estate And Accumulated Depreciation Construction Year	1,999
Real Estate And Accumulated Depreciation Year Of Acquisition	2,005
Depreciable Life (Years)	40 years
Philadelphia CBD [Member] | Cira Centre (2929 Arch Street) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	208,570,000
Net Improvements (Retirements) Since Acquisition	(13,907,000)
Carrying Amount at Which Carried [Abstract]
Land	12,586,000
Buildings and Improvements	182,077,000
Total	194,663,000
Accumulated Depreciation at December 31, 2018	$ 65,851,000
Real Estate And Accumulated Depreciation Construction Year	2,005
Depreciable Life (Years)	40 years
Philadelphia CBD [Member] | Three Logan Square (1717 Arch Street) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	98,188,000
Net Improvements (Retirements) Since Acquisition	63,532,000
Carrying Amount at Which Carried [Abstract]
Land	25,195,000
Buildings and Improvements	136,525,000
Total	161,720,000
Accumulated Depreciation at December 31, 2018	$ 34,908,000
Real Estate And Accumulated Depreciation Construction Year	1,990
Real Estate And Accumulated Depreciation Year Of Acquisition	2,010
Depreciable Life (Years)	40 years
Philadelphia CBD [Member] | Two Commerce Square (2001 Market Street) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 110,518,000
Initial Cost [Abstract]
Land	15,323,000
Buildings and Improvements	120,200,000
Net Improvements (Retirements) Since Acquisition	24,144,000
Carrying Amount at Which Carried [Abstract]
Land	15,323,000
Buildings and Improvements	144,344,000
Total	159,667,000
Accumulated Depreciation at December 31, 2018	$ 22,184,000
Real Estate And Accumulated Depreciation Construction Year	1,992
Real Estate And Accumulated Depreciation Year Of Acquisition	2,013
Depreciable Life (Years)	40 years
Philadelphia CBD [Member] | One Logan Square (130 North 18th Street) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	14,496,000
Buildings and Improvements	107,736,000
Net Improvements (Retirements) Since Acquisition	28,657,000
Carrying Amount at Which Carried [Abstract]
Land	14,473,000
Buildings and Improvements	136,416,000
Total	150,889,000
Accumulated Depreciation at December 31, 2018	$ 56,850,000
Real Estate And Accumulated Depreciation Construction Year	1,998
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	34 years
Philadelphia CBD [Member] | Two Logan Square (100 North 18th Street) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 82,805,000
Initial Cost [Abstract]
Land	16,066,000
Buildings and Improvements	100,255,000
Net Improvements (Retirements) Since Acquisition	19,053,000
Carrying Amount at Which Carried [Abstract]
Land	16,066,000
Buildings and Improvements	119,308,000
Total	135,374,000
Accumulated Depreciation at December 31, 2018	$ 45,211,000
Real Estate And Accumulated Depreciation Construction Year	1,988
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	36 years
Philadelphia CBD [Member] | One Commerce Square (2005 Market Street) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 120,183,000
Initial Cost [Abstract]
Land	15,161,000
Buildings and Improvements	105,021,000
Net Improvements (Retirements) Since Acquisition	27,997,000
Carrying Amount at Which Carried [Abstract]
Land	15,160,000
Buildings and Improvements	133,019,000
Total	148,179,000
Accumulated Depreciation at December 31, 2018	$ 19,848,000
Real Estate And Accumulated Depreciation Construction Year	1,987
Real Estate And Accumulated Depreciation Year Of Acquisition	2,013
Depreciable Life (Years)	40 years
Philadelphia CBD [Member] | Cira Centre South Garage (129 South 30th Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	76,008,000
Net Improvements (Retirements) Since Acquisition	14,183,000
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	90,191,000
Total	90,191,000
Accumulated Depreciation at December 31, 2018	$ 17,015,000
Real Estate And Accumulated Depreciation Construction Year	2,010
Depreciable Life (Years)	40 years
Philadelphia CBD [Member] | 1900 Market Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	7,768,000
Buildings and Improvements	17,263,000
Net Improvements (Retirements) Since Acquisition	51,364,000
Carrying Amount at Which Carried [Abstract]
Land	7,768,000
Buildings and Improvements	68,627,000
Total	76,395,000
Accumulated Depreciation at December 31, 2018	$ 11,327,000
Real Estate And Accumulated Depreciation Construction Year	1,981
Real Estate And Accumulated Depreciation Year Of Acquisition	2,012
Depreciable Life (Years)	30 years
Philadelphia CBD [Member] | 3020 Market Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	21,417,000
Net Improvements (Retirements) Since Acquisition	8,100,000
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	29,517,000
Total	29,517,000
Accumulated Depreciation at December 31, 2018	$ 9,013,000
Real Estate And Accumulated Depreciation Construction Year	1,959
Real Estate And Accumulated Depreciation Year Of Acquisition	2,011
Depreciable Life (Years)	26 years
Philadelphia CBD [Member] | The Lift at Juniper Street (101 - 103 Juniper Street) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	14,401,000
Net Improvements (Retirements) Since Acquisition	(14,401,000)
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	0
Total	0
Accumulated Depreciation at December 31, 2018	$ 0
Real Estate And Accumulated Depreciation Construction Year	2,010
Real Estate And Accumulated Depreciation Year Of Acquisition	2,006
Depreciable Life (Years)	40 years
Philadelphia CBD [Member] | 618-634 Market Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	13,365,000
Buildings and Improvements	5,791,000
Net Improvements (Retirements) Since Acquisition	1,952,000
Carrying Amount at Which Carried [Abstract]
Land	13,365,000
Buildings and Improvements	7,743,000
Total	21,108,000
Accumulated Depreciation at December 31, 2018	$ 4,601,000
Real Estate And Accumulated Depreciation Construction Year	1,966
Real Estate And Accumulated Depreciation Year Of Acquisition	2,015
Depreciable Life (Years)	5 years
Philadelphia CBD [Member] | FMC Tower at Cira Centre South (2929 Walnut Street) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	400,294,000
Net Improvements (Retirements) Since Acquisition	12,964,000
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	413,258,000
Total	413,258,000
Accumulated Depreciation at December 31, 2018	$ 31,439,000
Real Estate And Accumulated Depreciation Construction Year	2,016
Depreciable Life (Years)	40 years
Philadelphia CBD [Member] | 2100 Market Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	18,827,000
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	6,594,000
Carrying Amount at Which Carried [Abstract]
Land	18,854,000
Buildings and Improvements	6,567,000
Total	25,421,000
Accumulated Depreciation at December 31, 2018	$ 547,000
Real Estate And Accumulated Depreciation Year Of Acquisition	2,015
Philadelphia CBD [Member] | 3000 Market Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	18,924,000
Buildings and Improvements	13,080,000
Net Improvements (Retirements) Since Acquisition	600,000
Carrying Amount at Which Carried [Abstract]
Land	18,924,000
Buildings and Improvements	13,680,000
Total	32,604,000
Accumulated Depreciation at December 31, 2018	$ 1,720,000
Real Estate And Accumulated Depreciation Construction Year	1,937
Real Estate And Accumulated Depreciation Year Of Acquisition	2,017
Depreciable Life (Years)	12 years
Philadelphia CBD [Member] | The Bulletin Building (3025 Market Street) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	24,377,000
Net Improvements (Retirements) Since Acquisition	6,968,000
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	31,345,000
Total	31,345,000
Accumulated Depreciation at December 31, 2018	$ 978,000
Real Estate And Accumulated Depreciation Construction Year	1,953
Real Estate And Accumulated Depreciation Year Of Acquisition	2,017
Depreciable Life (Years)	40 years
Philadelphia CBD [Member] | 3001-3003 JFK Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	78,000
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	78,000
Total	78,000
Accumulated Depreciation at December 31, 2018	$ 2,000
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Philadelphia CBD [Member] | 3025 JFK Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	0
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	0
Total	0
Accumulated Depreciation at December 31, 2018	$ 0
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Metropolitan DC [Member] | 6600 Rockledge Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	37,421,000
Net Improvements (Retirements) Since Acquisition	9,349,000
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	46,770,000
Total	46,770,000
Accumulated Depreciation at December 31, 2018	$ 13,469,000
Real Estate And Accumulated Depreciation Construction Year	1,981
Real Estate And Accumulated Depreciation Year Of Acquisition	2,006
Depreciable Life (Years)	50 years
Metropolitan DC [Member] | 2340 Dulles Corner Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	82,248,000
Carrying Amount at Which Carried [Abstract]
Land	16,129,000
Buildings and Improvements	66,119,000
Total	82,248,000
Accumulated Depreciation at December 31, 2018	$ 20,429,000
Real Estate And Accumulated Depreciation Construction Year	1,987
Real Estate And Accumulated Depreciation Year Of Acquisition	2,006
Depreciable Life (Years)	40 years
Metropolitan DC [Member] | 1676 International Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	18,437,000
Buildings and Improvements	97,538,000
Net Improvements (Retirements) Since Acquisition	3,412,000
Carrying Amount at Which Carried [Abstract]
Land	18,785,000
Buildings and Improvements	100,602,000
Total	119,387,000
Accumulated Depreciation at December 31, 2018	$ 25,864,000
Real Estate And Accumulated Depreciation Construction Year	1,999
Real Estate And Accumulated Depreciation Year Of Acquisition	2,006
Depreciable Life (Years)	55 years
Metropolitan DC [Member] | 8260 Greensboro Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	7,952,000
Buildings and Improvements	33,964,000
Net Improvements (Retirements) Since Acquisition	4,559,000
Carrying Amount at Which Carried [Abstract]
Land	8,102,000
Buildings and Improvements	38,373,000
Total	46,475,000
Accumulated Depreciation at December 31, 2018	$ 10,083,000
Real Estate And Accumulated Depreciation Construction Year	1,980
Real Estate And Accumulated Depreciation Year Of Acquisition	2,006
Depreciable Life (Years)	52 years
Metropolitan DC [Member] | 2273 Research Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	5,167,000
Buildings and Improvements	31,110,000
Net Improvements (Retirements) Since Acquisition	4,538,000
Carrying Amount at Which Carried [Abstract]
Land	5,237,000
Buildings and Improvements	35,578,000
Total	40,815,000
Accumulated Depreciation at December 31, 2018	$ 10,624,000
Real Estate And Accumulated Depreciation Construction Year	1,999
Real Estate And Accumulated Depreciation Year Of Acquisition	2,006
Depreciable Life (Years)	45 years
Metropolitan DC [Member] | 2275 Research Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	5,059,000
Buildings and Improvements	29,668,000
Net Improvements (Retirements) Since Acquisition	8,034,000
Carrying Amount at Which Carried [Abstract]
Land	5,154,000
Buildings and Improvements	37,607,000
Total	42,761,000
Accumulated Depreciation at December 31, 2018	$ 12,388,000
Real Estate And Accumulated Depreciation Construction Year	1,990
Real Estate And Accumulated Depreciation Year Of Acquisition	2,006
Depreciable Life (Years)	45 years
Metropolitan DC [Member] | 2277 Research Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	4,649,000
Buildings and Improvements	26,952,000
Net Improvements (Retirements) Since Acquisition	18,854,000
Carrying Amount at Which Carried [Abstract]
Land	4,733,000
Buildings and Improvements	45,722,000
Total	50,455,000
Accumulated Depreciation at December 31, 2018	$ 14,723,000
Real Estate And Accumulated Depreciation Construction Year	1,986
Real Estate And Accumulated Depreciation Year Of Acquisition	2,006
Depreciable Life (Years)	45 years
Metropolitan DC [Member] | 1900 Gallows Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	7,797,000
Buildings and Improvements	47,817,000
Net Improvements (Retirements) Since Acquisition	(2,381,000)
Carrying Amount at Which Carried [Abstract]
Land	5,566,000
Buildings and Improvements	47,667,000
Total	53,233,000
Accumulated Depreciation at December 31, 2018	$ 19,418,000
Real Estate And Accumulated Depreciation Construction Year	1,989
Real Estate And Accumulated Depreciation Year Of Acquisition	2,006
Depreciable Life (Years)	52 years
Metropolitan DC [Member] | 8521 Leesburg Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	4,316,000
Buildings and Improvements	30,885,000
Net Improvements (Retirements) Since Acquisition	6,826,000
Carrying Amount at Which Carried [Abstract]
Land	4,397,000
Buildings and Improvements	37,630,000
Total	42,027,000
Accumulated Depreciation at December 31, 2018	$ 11,046,000
Real Estate And Accumulated Depreciation Construction Year	1,984
Real Estate And Accumulated Depreciation Year Of Acquisition	2,006
Depreciable Life (Years)	51 years
Austin, Texas [Member] | 11501 Burnet Road - Building 1 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,755,000
Buildings and Improvements	22,702,000
Net Improvements (Retirements) Since Acquisition	117,000
Carrying Amount at Which Carried [Abstract]
Land	3,755,000
Buildings and Improvements	22,819,000
Total	26,574,000
Accumulated Depreciation at December 31, 2018	$ 2,489,000
Real Estate And Accumulated Depreciation Construction Year	1,991
Real Estate And Accumulated Depreciation Year Of Acquisition	2,015
Depreciable Life (Years)	35 years
Austin, Texas [Member] | 11501 Burnet Road - Building 2 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,732,000
Buildings and Improvements	16,305,000
Net Improvements (Retirements) Since Acquisition	1,562,000
Carrying Amount at Which Carried [Abstract]
Land	2,732,000
Buildings and Improvements	17,867,000
Total	20,599,000
Accumulated Depreciation at December 31, 2018	$ 2,268,000
Real Estate And Accumulated Depreciation Construction Year	1,991
Real Estate And Accumulated Depreciation Year Of Acquisition	2,015
Depreciable Life (Years)	35 years
Austin, Texas [Member] | 11501 Burnet Road - Building 3 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,688,000
Buildings and Improvements	22,348,000
Net Improvements (Retirements) Since Acquisition	115,000
Carrying Amount at Which Carried [Abstract]
Land	3,688,000
Buildings and Improvements	22,463,000
Total	26,151,000
Accumulated Depreciation at December 31, 2018	$ 2,449,000
Real Estate And Accumulated Depreciation Construction Year	1,991
Real Estate And Accumulated Depreciation Year Of Acquisition	2,015
Depreciable Life (Years)	35 years
Austin, Texas [Member] | 11501 Burnet Road - Building 4 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,614,000
Buildings and Improvements	15,740,000
Net Improvements (Retirements) Since Acquisition	81,000
Carrying Amount at Which Carried [Abstract]
Land	2,614,000
Buildings and Improvements	15,821,000
Total	18,435,000
Accumulated Depreciation at December 31, 2018	$ 1,725,000
Real Estate And Accumulated Depreciation Construction Year	1,991
Real Estate And Accumulated Depreciation Year Of Acquisition	2,015
Depreciable Life (Years)	35 years
Austin, Texas [Member] | 11501 Burnet Road - Building 5 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,689,000
Buildings and Improvements	22,354,000
Net Improvements (Retirements) Since Acquisition	115,000
Carrying Amount at Which Carried [Abstract]
Land	3,689,000
Buildings and Improvements	22,469,000
Total	26,158,000
Accumulated Depreciation at December 31, 2018	$ 2,450,000
Real Estate And Accumulated Depreciation Construction Year	1,991
Real Estate And Accumulated Depreciation Year Of Acquisition	2,015
Depreciable Life (Years)	35 years
Austin, Texas [Member] | 11501 Burnet Road - Building 6 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,676,000
Buildings and Improvements	15,972,000
Net Improvements (Retirements) Since Acquisition	13,396,000
Carrying Amount at Which Carried [Abstract]
Land	2,676,000
Buildings and Improvements	29,368,000
Total	32,044,000
Accumulated Depreciation at December 31, 2018	$ 1,387,000
Real Estate And Accumulated Depreciation Construction Year	1,991
Real Estate And Accumulated Depreciation Year Of Acquisition	2,015
Depreciable Life (Years)	40 years
Austin, Texas [Member] | 11501 Burnet Road - Building 8 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,400,000
Buildings and Improvements	7,422,000
Net Improvements (Retirements) Since Acquisition	100,000
Carrying Amount at Which Carried [Abstract]
Land	1,400,000
Buildings and Improvements	7,522,000
Total	8,922,000
Accumulated Depreciation at December 31, 2018	$ 828,000
Real Estate And Accumulated Depreciation Construction Year	1,991
Real Estate And Accumulated Depreciation Year Of Acquisition	2,015
Depreciable Life (Years)	35 years
Austin, Texas [Member] | 11501 Burnet Road - Parking Garage [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	19,826,000
Net Improvements (Retirements) Since Acquisition	102,000
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	19,928,000
Total	19,928,000
Accumulated Depreciation at December 31, 2018	$ 2,884,000
Real Estate And Accumulated Depreciation Construction Year	1,991
Real Estate And Accumulated Depreciation Year Of Acquisition	2,015
Depreciable Life (Years)	35 years
Austin, Texas [Member] | One Barton Skyway (1501 South MoPac Expressway) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	10,496,000
Buildings and Improvements	47,670,000
Net Improvements (Retirements) Since Acquisition	(39,000)
Carrying Amount at Which Carried [Abstract]
Land	10,495,000
Buildings and Improvements	47,632,000
Total	58,127,000
Accumulated Depreciation at December 31, 2018	$ 103,000
Real Estate And Accumulated Depreciation Construction Year	1,999
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | Two Barton Skyway (1601 South MoPac Expressway) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	10,849,000
Buildings and Improvements	53,868,000
Net Improvements (Retirements) Since Acquisition	(40,000)
Carrying Amount at Which Carried [Abstract]
Land	10,848,000
Buildings and Improvements	53,829,000
Total	64,677,000
Accumulated Depreciation at December 31, 2018	$ 116,000
Real Estate And Accumulated Depreciation Construction Year	2,000
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | Three Barton Skyway (1221 South MoPac Expressway) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	10,374,000
Buildings and Improvements	47,624,000
Net Improvements (Retirements) Since Acquisition	(39,000)
Carrying Amount at Which Carried [Abstract]
Land	10,373,000
Buildings and Improvements	47,586,000
Total	57,959,000
Accumulated Depreciation at December 31, 2018	$ 100,000
Real Estate And Accumulated Depreciation Construction Year	2,001
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | Four Barton Skyway (1301 South MoPac Expressway) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	13,301,000
Buildings and Improvements	57,041,000
Net Improvements (Retirements) Since Acquisition	(40,000)
Carrying Amount at Which Carried [Abstract]
Land	13,300,000
Buildings and Improvements	57,002,000
Total	70,302,000
Accumulated Depreciation at December 31, 2018	$ 121,000
Real Estate And Accumulated Depreciation Construction Year	2,001
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | Four Points Centre (11305 Four Points Drive) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	7,800,000
Buildings and Improvements	43,581,000
Net Improvements (Retirements) Since Acquisition	(40,000)
Carrying Amount at Which Carried [Abstract]
Land	7,800,000
Buildings and Improvements	43,541,000
Total	51,341,000
Accumulated Depreciation at December 31, 2018	$ 91,000
Real Estate And Accumulated Depreciation Construction Year	2,008
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | River Place - Building 1 (6500 River Place Boulevard) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,004,000
Buildings and Improvements	17,680,000
Net Improvements (Retirements) Since Acquisition	(39,000)
Carrying Amount at Which Carried [Abstract]
Land	2,004,000
Buildings and Improvements	17,641,000
Total	19,645,000
Accumulated Depreciation at December 31, 2018	$ 36,000
Real Estate And Accumulated Depreciation Construction Year	2,000
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | River Place - Building 2 (6500 River Place Boulevard) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,137,000
Buildings and Improvements	29,254,000
Net Improvements (Retirements) Since Acquisition	(40,000)
Carrying Amount at Which Carried [Abstract]
Land	3,137,000
Buildings and Improvements	29,214,000
Total	32,351,000
Accumulated Depreciation at December 31, 2018	$ 61,000
Real Estate And Accumulated Depreciation Construction Year	2,000
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | River Place - Building 3 (6500 River Place Boulevard) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,064,000
Buildings and Improvements	26,705,000
Net Improvements (Retirements) Since Acquisition	(40,000)
Carrying Amount at Which Carried [Abstract]
Land	3,064,000
Buildings and Improvements	26,665,000
Total	29,729,000
Accumulated Depreciation at December 31, 2018	$ 56,000
Real Estate And Accumulated Depreciation Construction Year	2,000
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | River Place - Building 4 (6500 River Place Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,273,000
Buildings and Improvements	18,617,000
Net Improvements (Retirements) Since Acquisition	(39,000)
Carrying Amount at Which Carried [Abstract]
Land	2,273,000
Buildings and Improvements	18,578,000
Total	20,851,000
Accumulated Depreciation at December 31, 2018	$ 39,000
Real Estate And Accumulated Depreciation Construction Year	2,000
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | River Place - Building 5 (6500 River Place Boulevard) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,752,000
Buildings and Improvements	14,315,000
Net Improvements (Retirements) Since Acquisition	(39,000)
Carrying Amount at Which Carried [Abstract]
Land	1,752,000
Buildings and Improvements	14,276,000
Total	16,028,000
Accumulated Depreciation at December 31, 2018	$ 30,000
Real Estate And Accumulated Depreciation Construction Year	2,001
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | River Place - Building 6 (6500 River Place Boulevard) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,598,000
Buildings and Improvements	12,945,000
Net Improvements (Retirements) Since Acquisition	(39,000)
Carrying Amount at Which Carried [Abstract]
Land	1,598,000
Buildings and Improvements	12,906,000
Total	14,504,000
Accumulated Depreciation at December 31, 2018	$ 27,000
Real Estate And Accumulated Depreciation Construction Year	2,001
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | River Place - Building 7 (6500 River Place Boulevard) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	1,801,000
Buildings and Improvements	16,486,000
Net Improvements (Retirements) Since Acquisition	(39,000)
Carrying Amount at Which Carried [Abstract]
Land	1,801,000
Buildings and Improvements	16,447,000
Total	18,248,000
Accumulated Depreciation at December 31, 2018	$ 35,000
Real Estate And Accumulated Depreciation Construction Year	2,002
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Austin, Texas [Member] | Quarry Lake II (4516 Seton Center Parkway) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	3,970,000
Buildings and Improvements	30,546,000
Net Improvements (Retirements) Since Acquisition	604,000
Carrying Amount at Which Carried [Abstract]
Land	3,867,000
Buildings and Improvements	31,253,000
Total	35,120,000
Accumulated Depreciation at December 31, 2018	$ 0
Real Estate And Accumulated Depreciation Construction Year	1,998
Real Estate And Accumulated Depreciation Year Of Acquisition	2,018
Depreciable Life (Years)	40 years
Other [Member] | 10 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	244,000
Buildings and Improvements	971,000
Net Improvements (Retirements) Since Acquisition	69,000
Carrying Amount at Which Carried [Abstract]
Land	244,000
Buildings and Improvements	1,040,000
Total	1,284,000
Accumulated Depreciation at December 31, 2018	$ 597,000
Real Estate And Accumulated Depreciation Construction Year	1,983
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
Other [Member] | 7 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	231,000
Buildings and Improvements	921,000
Net Improvements (Retirements) Since Acquisition	31,000
Carrying Amount at Which Carried [Abstract]
Land	231,000
Buildings and Improvements	952,000
Total	1,183,000
Accumulated Depreciation at December 31, 2018	$ 522,000
Real Estate And Accumulated Depreciation Construction Year	1,983
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
Other [Member] | 2 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	185,000
Buildings and Improvements	730,000
Net Improvements (Retirements) Since Acquisition	11,000
Carrying Amount at Which Carried [Abstract]
Land	185,000
Buildings and Improvements	741,000
Total	926,000
Accumulated Depreciation at December 31, 2018	$ 741,000
Real Estate And Accumulated Depreciation Construction Year	1,974
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
Other [Member] | 4 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	183,000
Buildings and Improvements	726,000
Net Improvements (Retirements) Since Acquisition	6,000
Carrying Amount at Which Carried [Abstract]
Land	183,000
Buildings and Improvements	732,000
Total	915,000
Accumulated Depreciation at December 31, 2018	$ 732,000
Real Estate And Accumulated Depreciation Construction Year	1,974
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
Other [Member] | 1 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	93,000
Buildings and Improvements	364,000
Net Improvements (Retirements) Since Acquisition	8,000
Carrying Amount at Which Carried [Abstract]
Land	93,000
Buildings and Improvements	372,000
Total	465,000
Accumulated Depreciation at December 31, 2018	$ 372,000
Real Estate And Accumulated Depreciation Construction Year	1,972
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
Other [Member] | 5 U.S. Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	21,000
Buildings and Improvements	81,000
Net Improvements (Retirements) Since Acquisition	2,000
Carrying Amount at Which Carried [Abstract]
Land	21,000
Buildings and Improvements	83,000
Total	104,000
Accumulated Depreciation at December 31, 2018	$ 59,000
Real Estate And Accumulated Depreciation Construction Year	1,987
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
Other [Member] | 5 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	9,000
Buildings and Improvements	32,000
Net Improvements (Retirements) Since Acquisition	3,000
Carrying Amount at Which Carried [Abstract]
Land	9,000
Buildings and Improvements	35,000
Total	44,000
Accumulated Depreciation at December 31, 2018	$ 25,000
Real Estate And Accumulated Depreciation Construction Year	1,968
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
Other [Member] | Main Street-Plaza 1000 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	2,732,000
Buildings and Improvements	10,942,000
Net Improvements (Retirements) Since Acquisition	376,000
Carrying Amount at Which Carried [Abstract]
Land	2,732,000
Buildings and Improvements	11,318,000
Total	14,050,000
Accumulated Depreciation at December 31, 2018	$ 11,064,000
Real Estate And Accumulated Depreciation Construction Year	1,988
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
Other [Member] | Main Street-Piazza [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	696,000
Buildings and Improvements	2,802,000
Net Improvements (Retirements) Since Acquisition	3,701,000
Carrying Amount at Which Carried [Abstract]
Land	705,000
Buildings and Improvements	6,494,000
Total	7,199,000
Accumulated Depreciation at December 31, 2018	$ 3,124,000
Real Estate And Accumulated Depreciation Construction Year	1,990
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
Other [Member] | Main Street-Promenade [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	532,000
Buildings and Improvements	2,052,000
Net Improvements (Retirements) Since Acquisition	405,000
Carrying Amount at Which Carried [Abstract]
Land	532,000
Buildings and Improvements	2,457,000
Total	2,989,000
Accumulated Depreciation at December 31, 2018	$ 1,445,000
Real Estate And Accumulated Depreciation Construction Year	1,988
Real Estate And Accumulated Depreciation Year Of Acquisition	1,997
Depreciable Life (Years)	40 years
Other [Member] | 920 North King Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	6,141,000
Buildings and Improvements	21,140,000
Net Improvements (Retirements) Since Acquisition	7,969,000
Carrying Amount at Which Carried [Abstract]
Land	6,141,000
Buildings and Improvements	29,109,000
Total	35,250,000
Accumulated Depreciation at December 31, 2018	$ 11,593,000
Real Estate And Accumulated Depreciation Construction Year	1,989
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	30 years
Other [Member] | 300 Delaware Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Initial Cost [Abstract]
Land	6,369,000
Buildings and Improvements	13,739,000
Net Improvements (Retirements) Since Acquisition	1,991,000
Carrying Amount at Which Carried [Abstract]
Land	6,369,000
Buildings and Improvements	15,729,000
Total	22,099,000
Accumulated Depreciation at December 31, 2018	$ 8,202,000
Real Estate And Accumulated Depreciation Construction Year	1,989
Real Estate And Accumulated Depreciation Year Of Acquisition	2,004
Depreciable Life (Years)	23 years

Schedule III - Real Estate an_3

Schedule III - Real Estate and Accumulated Depreciation (Reconciliation of Real Estate Investments and Accumulated Depreciation) (Parentheticals) (Details)		12 Months Ended
		Dec. 31, 2018USD ($)Parcel	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at the Beginning of the Year		$ 3,832,348,000	$ 3,659,886,000	$ 4,487,588,000
Additions:
Acquisitions		509,654,000	62,586,000	0
Capital expenditures and assets placed into service		129,274,000	356,857,000	213,996,000
Less:
Dispositions/impairments/placed into redevelopment		(469,441,000)	(189,395,000)	(962,676,000)
Retirements		(48,516,000)	(57,586,000)	(79,022,000)
Balance at the end of the year		3,953,319,000	3,832,348,000	3,659,886,000
Assets held for sale	[1]	0	0	(73,591,000)
Operating properties		3,953,319,000	3,832,348,000	3,586,295,000
Tax Basis of Assets, Cost for Income Tax Purposes		3,300,000,000	3,100,000,000
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the beginning of the year		895,091,000	885,392,000	1,080,616,000
Real Estate Accumulated Depreciation Additions [Abstract]
Depreciation expense		135,473,000	135,822,000	131,859,000
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Dispositions/impairments/placed into redevelopment		(117,589,000)	(74,178,000)	(250,110,000)
Retirements		(47,513,000)	(51,945,000)	(76,973,000)
Balance at the end of the year		865,462,000	895,091,000	885,392,000
Assets held for sale		0	0	(32,916,000)
Real Estate Investment Property, Accumulated Depreciation		$ 865,462,000	895,091,000
Land Parcel One [Member]
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Lease agreement term		99 years
Land Parcel Two [Member]
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Lease agreement term		99 years
Leashold Interest Land [Member]
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Number of Parcels | Parcel		2
Philadelphia CBD [Member] | 618-634 Market Street [Member]
Less:
Balance at the end of the year		$ 21,108,000
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Balance at the end of the year		$ 4,601,000
Useful life		5 years
Philadelphia CBD [Member] | 618-634 Market Street [Member] | Parking Structure [Member]
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Useful life		5 years
Accumulated Depreciation, including HFS [Member]
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Real Estate Investment Property, Accumulated Depreciation		$ 865,462,000	$ 895,091,000	$ 852,476,000
[1]	As of December 31, 2016, three office properties in the Metropolitan Washington, D.C. segment and two office properties in the Other segment were classified as held for sale in accordance with applicable accounting standards for long-lived assets. See the “ 2016 ” section of Note 3, “Real Estate Investments,” for further information.