Name:	fsp_EffectiveRevisedTexasFranchiseTaxRate
Namespace Prefix:	fsp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The portion of the difference between total income tax expense or benefit as reported in the income statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to the Revised Texas Franchise Tax.

No definition available.

Name:	fsp_IncomeTaxReconciliationRevisedTexasFranchiseTax
Namespace Prefix:	fsp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the maximum ownership in all Taxable REIT Subsidiaries that can be held by the entity as a percentage of its assets value to maintain its REIT status.

No definition available.

Name:	fsp_MaximumOwnershipInAllTaxableREITSubsidiariesAsPercentageOfAssetsOfEntityToMaintainREITStatus
Namespace Prefix:	fsp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the maximum ownership in all Taxable REIT Subsidiaries that can be held by the entity as a percentage of its assets value when considered together with other non-real estate assets to maintain its REIT status.

No definition available.

Name:	fsp_MaximumOwnershipInAllTaxableREITSubsidiariesAsPercentageOfAssetsOfEntityToMaintainREITStatusIncludingOtherNonRealEstateAssets
Namespace Prefix:	fsp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the maximum ownership that the entity can hold as a percentage of the voting power or value of the securities of each issuer which is not a REIT or Taxable REIT Subsidiary.

No definition available.

Name:	fsp_MaximumOwnershipPercentageInEachIssuerOtherThanREITOrTRSToMaintainREITStatus
Namespace Prefix:	fsp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	fsp_OperatingLossCarryforwardAbstract
Namespace Prefix:	fsp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the period after which the net operating losses expire.

No definition available.

Name:	fsp_OperatingLossCarryforwardsExpirationPeriod
Namespace Prefix:	fsp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the period of statute of limitations for the entity's income tax returns, that remain subject to examination.

No definition available.

Name:	fsp_PeriodOfStatuteOfLimitations
Namespace Prefix:	fsp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the excess of tax basis over book basis of real estate assets.

No definition available.

Name:	fsp_RealEstateAssetsDifferencesBetweenBookAndTaxBasis
Namespace Prefix:	fsp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a),(b)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 45

-Subparagraph a, b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Article 4

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Income Tax Expense (or Benefit)

-URI http://asc.fasb.org/extlink&oid=6515339

Name:	us-gaap_IncomeTaxExpenseBenefit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The sum of other amounts reflected in the reconciliation of the statutory tax provision (benefit) to the actual tax provision (benefit).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32687-109319

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319

Name:	us-gaap_IncomeTaxReconciliationOtherReconcilingItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The sum of domestic, foreign and state and local operating loss carryforwards, before tax effects, available to reduce future taxable income under enacted tax laws.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32559-109319

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 48

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.