Name:	fsp_DisposalGroupIncludingDiscontinuedOperationDeferredCostsLeasingNet
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Amount classified as real estate investment property, net, attributable to disposal group held for sale or disposed of.

No definition available.

Name:	fsp_DisposalGroupIncludingDiscontinuedOperationRealEstateInvestmentPropertyNet
Namespace Prefix:	fsp_
Data Type:	xbrli:monetaryItemType
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Amount classified as straight line rents receivable, attributable to disposal group held for sale or disposed of.

No definition available.

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

The expected amount of gain (loss) on sale of properties.

No definition available.

Name:	fsp_ExpectedGainLossOnSaleOfProperties
Namespace Prefix:	fsp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Expected sales price of a property.

No definition available.

Name:	fsp_ExpectedSalesPriceOfProperty
Namespace Prefix:	fsp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Represents the number of office properties sold.

No definition available.

Name:	fsp_NumberOfPropertiesSold
Namespace Prefix:	fsp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The cash outflow for the costs related to the sale of property held for sale.

No definition available.

Name:	fsp_PaymentForCostsRelatedToSalePropertyHeldForSale
Namespace Prefix:	fsp_
Data Type:	xbrli:monetaryItemType
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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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Amount of assets held-for-sale that are not part of a disposal group.

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This element represents costs incurred by the lessor that are (a) costs to originate a lease incurred in transactions with independent third parties that (i) result directly from and are essential to acquire that lease and (ii) would not have been incurred had that leasing transaction not occurred and (b) certain costs directly related to specified activities performed by the lessor for that lease. Those activities are: evaluating the prospective lessee's financial condition; evaluating and recording guarantees, collateral, and other security arrangements; negotiating lease terms; preparing and processing lease documents; and closing the transaction. This element is net of accumulated amortization.

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Amount of excess of rental income recognized over rental payment required by lease.

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-Name Accounting Standards Codification
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Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

No definition available.

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration
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The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

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-Topic 230
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-Name Accounting Standards Codification
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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.

No definition available.

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
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The cash inflow from the sale of formerly productive land held for sale, anything permanently fixed to it, including buildings, structures on it, and so forth.

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Data Type:	xbrli:monetaryItemType
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Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(d))
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-Topic 944
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-Name Accounting Standards Codification
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Name:	us-gaap_RealEstateInvestmentPropertyNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=fsp_PropertyInGlenAllenVirginiaMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
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