Represents the acquisition fees incurred by the entity and excluded during the reporting period.

No definition available.

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Balance Type:	debit
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- Definition

Represents the commission incurred by the entity and excluded during the reporting period.

+ References

No definition available.

+ Details

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- Definition

This item represents disclosure of the amount of dividends or other distributions received from unconsolidated subsidiaries, certain corporate joint ventures, and certain noncontrolled corporation; these investments are accounted for under the equity method of accounting. This element includes distributions that constitute a return of investment.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Represents the percentage of the equity method investee's outstanding preferred stock purchased by the entity during the reporting period.

+ References

No definition available.

+ Details

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Namespace Prefix:	fsp_
Data Type:	num:percentItemType
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- Definition

The number of preferred stock purchased in the investee accounted for under the equity method of accounting.

+ References

No definition available.

+ Details

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- Definition

Represents the offering price of preferred stock purchased in the investee accounted for under the equity method of accounting.

+ References

No definition available.

+ Details

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- Definition

Represents the cost of preferred stock purchased in the investee accounted for under the equity method of accounting, net of commission and fees paid.

+ References

No definition available.

+ Details

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Namespace Prefix:	fsp_
Data Type:	xbrli:monetaryItemType
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- Definition

Represents the loan fees incurred by the entity and excluded during the reporting period.

+ References

No definition available.

+ Details

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

This item represents the amount of gain (loss) arising from the disposal of an equity method investment.

+ References

No definition available.

+ Details

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.12)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 2: 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=6943989&loc=d3e3602-108585

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 9

-Article 5

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 11

-Article 7

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 6

-Subparagraph 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 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 19

-Subparagraph c

-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.

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Related Party Transactions and Investments in Non-Consolidated Entities (Details 2) (USD $)	3 Months Ended		0 Months Ended	1 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended		1 Months Ended	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 20, 2012 FSP Phoenix Tower Corp	Sep. 30, 2006 FSP Phoenix Tower Corp	Mar. 31, 2012 FSP Phoenix Tower Corp	Dec. 31, 2007 East Wacker	Mar. 31, 2013 East Wacker	Mar. 31, 2012 East Wacker	May 31, 2009 Grand Boulevard	Mar. 31, 2013 Grand Boulevard	Mar. 31, 2012 Grand Boulevard
Sponsored REITs
Equity in earnings (loss)	$ (187,000)	$ 391,000			$ 3,000		$ (110,000)	$ 439,000		$ (77,000)	$ (51,000)
Gain resulted from sale of property			1,582,000
Preferred shares purchased				48		965.75			175.5
Percentage of outstanding preferred shares purchased				4.60%		43.70%			27.00%
Net cost of preferred shares purchased						82,813,000			15,049,000
Offering price of preferred shares purchased						96,575,000			17,550,000
Commissions excluded						7,726,000			1,404,000
Loan fees excluded						5,553,000			1,009,000
Acquisition fees excluded						483,000			88,000
Distributions received from non-consolidated REITs
Distributions from non-consolidated REITs	$ 27,000	$ 929,000