Business Acquisition Year

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- Definition

Business Combination, Number of Acquisitions

+ References

No definition available.

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- Definition

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Below Market Lease

+ References

No definition available.

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- Definition

Name of Property

+ References

No definition available.

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- Definition

Number Of Properties Acquired

+ References

No definition available.

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- Definition

Amount of amortization of acquired leases acquired as part of a real property acquisition at below market lease rate with a finite life.

+ References

No definition available.

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- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

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- Definition

Area of a real estate property.

+ References

No definition available.

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- Definition

Amount of accumulated amortization of leases acquired as part of a real property acquisition at below market lease rate with a finite life.

+ References

No definition available.

+ Details

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- Definition

Amount before amortization of leases acquired as part of a real property acquisition at below market lease rate with a finite life.

+ References

No definition available.

+ Details

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- Definition

Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

+ References

No definition available.

+ Details

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- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 30

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 30

-Paragraph 8

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

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- Definition

Amount of facility held for productive use including, but not limited to, office, production, storage and distribution facilities, acquired at the acquisition date.

+ References

+ Details

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- Definition

The amount of identifiable intangible assets recognized as of the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 55

-Paragraph 37

-URI http://asc.fasb.org/extlink&oid=35744172&loc=d3e2207-128464

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- Definition

Amount of real estate acquired, at the acquisition date.

+ References

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- Definition

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

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- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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Real Estate Acquired - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014 property	Dec. 31, 2013 Property	Dec. 31, 2012 Property	Dec. 31, 2012	Jan. 31, 2014	Apr. 30, 2014	Dec. 31, 2014	Aug. 31, 2014	Aug. 31, 2013 sqft	Dec. 31, 2013 sqft
Business Acquisition [Line Items]
Aggregate cost	$ 68,000,000	$ 5,100,000	$ 34,100,000
Property acquisition costs	900,000	106,000	1,100,000	1,100,000			900,000			106,000
Number of properties acquired	5						5
Number of properties acquired		2bfs_NumberOfPropertiesAcquired	2bfs_NumberOfPropertiesAcquired	2bfs_NumberOfPropertiesAcquired						2bfs_NumberOfPropertiesAcquired
Purchase price allocated to buildings	4,873,000	2,000,000	3,800,000	3,800,000			4,873,000			2,000,000
Purchase price allocated to land	66,047,000	3,100,000	30,400,000	30,400,000			66,047,000			3,100,000
Purchase price allocated to below market lease	5,069,000		700,000	700,000			5,069,000
Business acquisition, intangible asset estimated useful life			3 years 1 month 6 days
Intangible liabilities gross carrying amount	29,900,000us-gaap_BelowMarketLeaseGross	24,800,000us-gaap_BelowMarketLeaseGross					29,900,000us-gaap_BelowMarketLeaseGross			24,800,000us-gaap_BelowMarketLeaseGross
Intangible liabilities, accumulated amortization	11,900,000	10,000,000					11,900,000			10,000,000
Accretion income, intangible liabilities	1,900,000us-gaap_AmortizationOfBelowMarketLease	1,700,000us-gaap_AmortizationOfBelowMarketLease	1,600,000us-gaap_AmortizationOfBelowMarketLease
In-Place Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	2,099,000		500,000	500,000			2,099,000
Above Market Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	0						0
Intangible assets gross carrying amount	1,000,000	1,000,000					1,000,000			1,000,000
Intangible assets, accumulated amortization	996,700	974,100					996,700			974,100
Amortization expense of intangible assets	23,000	45,000	60,000
Lease Acquisition Costs
Business Acquisition [Line Items]
Intangible assets gross carrying amount	24,000,000	21,900,000					24,000,000			21,900,000
Intangible assets, accumulated amortization	18,000,000	16,700,000					18,000,000			16,700,000
Amortization expense of intangible assets	1,300,000	2,000,000	2,000,000
1500 Rockville Pike
Business Acquisition [Line Items]
Year of acquisition				Dec. 31, 2012
Aggregate cost				22,400,000
Name of property				1500 Rockville Pike
Property acquisition costs			600,000	600,000
1580 Rockville Pike
Business Acquisition [Line Items]
Year of acquisition					Jan. 31, 2014
Aggregate cost					8,000,000
Name of property					1580 Rockville Pike
Property acquisition costs					200,000
Purchase price allocated to buildings	2,200,000						2,200,000
Purchase price allocated to land	9,600,000						9,600,000
Purchase price allocated to below market lease	4,313,000						4,313,000
1580 Rockville Pike \| In-Place Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	513,000						513,000
1580 Rockville Pike \| Above Market Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	0						0
1582 Rockville Pike
Business Acquisition [Line Items]
Year of acquisition						Apr. 30, 2014
Aggregate cost						11,000,000
Name of property						1582 Rockville Pike
Property acquisition costs						200,000
Purchase price allocated to buildings	828,000						828,000
Purchase price allocated to land	9,742,000						9,742,000
Purchase price allocated to below market lease	419,000						419,000
1582 Rockville Pike \| In-Place Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	849,000						849,000
1582 Rockville Pike \| Above Market Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	0						0
1584 Rockville Pike
Business Acquisition [Line Items]
Year of acquisition							Dec. 31, 2014
Aggregate cost							6,200,000
Name of property							1584 Rockville Pike
Property acquisition costs	200,000						200,000
Purchase price allocated to buildings	440,000						440,000
Purchase price allocated to land	5,798,000						5,798,000
Purchase price allocated to below market lease	337,000						337,000
1584 Rockville Pike \| In-Place Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	249,000						249,000
1584 Rockville Pike \| Above Market Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	0						0
750 N. Glebe Road
Business Acquisition [Line Items]
Year of acquisition								Aug. 31, 2014
Aggregate cost								40,000,000
Name of property								750 N. Glebe Road
Property acquisition costs								400,000
Purchase price allocated to buildings	1,327,000						1,327,000
Purchase price allocated to land	38,224,000						38,224,000
Purchase price allocated to below market lease	0						0
750 N. Glebe Road \| In-Place Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	449,000						449,000
750 N. Glebe Road \| Above Market Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	0						0
730 N. Glebe Road
Business Acquisition [Line Items]
Year of acquisition							Dec. 31, 2014
Aggregate cost							2,800,000
Name of property							730 N. Glebe Road
Property acquisition costs	40,400						40,400
Purchase price allocated to buildings	78,000						78,000
Purchase price allocated to land	2,683,000						2,683,000
Purchase price allocated to below market lease	0						0
730 N. Glebe Road \| In-Place Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	39,000						39,000
730 N. Glebe Road \| Above Market Leases
Business Acquisition [Line Items]
Purchase price allocated to leases	0						0
5541 Nicholson Lane
Business Acquisition [Line Items]
Year of acquisition				Dec. 31, 2012
Aggregate cost				11,700,000
Name of property				5541 Nicholson Lane
Property acquisition costs			500,000	500,000
Kentlands Pad
Business Acquisition [Line Items]
Year of acquisition									Aug. 31, 2013
Aggregate cost									4,300,000
Property acquisition costs									106,000
Area of real estate property (in square feet)									7,100
Hunt Club Pad
Business Acquisition [Line Items]
Year of acquisition										Dec. 31, 2013
Aggregate cost										$ 800,000
Area of real estate property (in square feet)		5,500								5,500