Percentage points added to the reference rate to compute the variable rate on the debt instrument at period end.

No definition available.

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- Definition

Maximum amount of additional loans that may be issued under the accordion feature of the debt agreement subject to receipt of lender commitments and satisfaction of certain customary conditions.

+ References

No definition available.

+ Details

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Namespace Prefix:	fsp_
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Balance Type:	credit
Period Type:	instant

- Definition

Representing fixed charge coverage ratio.

+ References

No definition available.

+ Details

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Namespace Prefix:	fsp_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

The length of time the company can extend the maturity date on the debt revolver.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The increase in the maximum borrowing capacity under the credit facility upon exercise of the accordion feature which is subject to receipt of lender commitments and satisfaction of certain customary conditions.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

The number of periods the company can extend the maturity date of the debt revolver.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Represents the unsecured leverage ratio that must be maintained as a part of the debt agreement.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Represents the leverage ratio for a significant acquisition in a short period of time.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
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-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Balance Type:	na
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- Definition

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

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of liability hedged in fair value hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109999712-113959

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The effective interest rate at the end of the reporting period.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-SubTopic 10
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Bank Note Payable, Term Loans Payable and Senior Notes (Details)		6 Months Ended
	Sep. 27, 2012 USD ($)	Jun. 30, 2020 USD ($) period	Dec. 31, 2019 USD ($)	Aug. 02, 2018 USD ($)
Debt Instrument [Line Items]
Portion of future LIBOR-based rate risk		$ 23,000,000.0
Borrowings outstanding		30,000,000
Senior Notes
Debt Instrument [Line Items]
Principal amount of loan		$ 200,000,000
Fixed charge coverage ratio		1.50
Series A Notes
Debt Instrument [Line Items]
Principal amount of loan		$ 116,000,000
Interest rate (as a percent)		3.99%
Series B Notes
Debt Instrument [Line Items]
Principal amount of loan		$ 84,000,000
Interest rate (as a percent)		4.26%
Maximum \| Senior Notes
Debt Instrument [Line Items]
Unsecured leverage ratio		60.00%
Unsecured leverage ratio for significant acquisition		65.00%
BAML Revolver
Debt Instrument [Line Items]
Weighted average interest rate (as a percent)		2.01%	3.67%
Effective interest rate (as a percent)		1.36%
Total available		$ 600,000,000
Number of periods of extension \| period		2
Length of extension period		6 months
Additional borrowing capacity allowed by exercising an accordion feature		$ 500,000,000
Borrowings outstanding		$ 30,000,000	$ 0
Facility fee at period end (as a percent)		0.25%
BAML Revolver \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		1.20%
BAML Revolver \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		0.20%
BAML Term Loan
Debt Instrument [Line Items]
Principal amount of loan		$ 400,000,000
Effective interest rate (as a percent)		2.47%
Additional borrowing capacity allowed by exercising an accordion feature		$ 500,000,000
Amount drawn down	$ 400,000,000
BAML Term Loan \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		1.35%
Fixed rate (as a percent)		1.12%
BAML Term Loan \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		0.35%
JPM Term Loan
Debt Instrument [Line Items]
Principal amount of loan				$ 150,000,000
Portion of future LIBOR-based rate risk		$ 100,000,000
JPM Term Loan \| Hedged portion
Debt Instrument [Line Items]
Portion of future LIBOR-based rate risk		$ 100,000,000
Effective interest rate (as a percent)		3.69%
JPM Term Loan \| Unhedged portion
Debt Instrument [Line Items]
Weighted average interest rate (as a percent)		2.36%	3.54%
Portion of future LIBOR-based rate risk		$ 50,000,000
Effective interest rate (as a percent)		1.44%
JPM Term Loan \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		1.25%
JPM Term Loan \| LIBOR \| Hedged portion
Debt Instrument [Line Items]
Fixed rate (as a percent)		2.44%
JPM Term Loan \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		0.25%
BMO Term Loan
Debt Instrument [Line Items]
Principal amount of loan		$ 220,000,000
Additional loans allowed by exercising an accordion feature		$ 100,000,000
Effective interest rate (as a percent)		3.57%
BMO Term Loan \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		1.25%
Fixed rate (as a percent)		2.32%
BMO Term Loan \| LIBOR \| Hedged portion
Debt Instrument [Line Items]
Fixed rate (as a percent)		2.39%
BMO Term Loan \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		0.25%
Tranche A Term Loan
Debt Instrument [Line Items]
Principal amount of loan		$ 55,000,000
Tranche B Term Loan
Debt Instrument [Line Items]
Principal amount of loan		$ 165,000,000