Indebtedness - Mortgage Loans Obtained (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012 Property sqft
Mortgage Loans on Real Estate [Line Items]
Loan Principal	$ 280,317
Property Carrying Value	319,685
Mortgage Financing VII - XIV [Member]
Mortgage Loans on Real Estate [Line Items]
Loan Principal	178,300
Interest Rate	4.45%
Origination Date	May 02, 2011
Maturity Date	Jun. 01, 2018
Amortization Period	30 years
Number of Industrial Properties Collateralizing Mortgage	32
GLA	5,900,000
Property Carrying Value	206,291
Mortgage Financing XV [Member]
Mortgage Loans on Real Estate [Line Items]
Loan Principal	24,417
Interest Rate	5.579%
Origination Date	May 26, 2011
Maturity Date	Feb. 01, 2016
Amortization Period	30 years
Number of Industrial Properties Collateralizing Mortgage	1
GLA	700,000
Property Carrying Value	28,991
Mortgage Financing XVI - XXVI [Member]
Mortgage Loans on Real Estate [Line Items]
Loan Principal	77,600
Interest Rate	4.85%
Origination Date	Sep. 23, 2011
Maturity Date	Oct. 01, 2021
Amortization Period	30 years
Number of Industrial Properties Collateralizing Mortgage	24
GLA	2,300,000
Property Carrying Value	84,403
Mortgage Financing I - VI [Member]
Mortgage Loans on Real Estate [Line Items]
Loan Principal	100,599
Interest Rate	4.03%
Origination Date	Aug. 29, 2012
Maturity Date	Sep. 01, 2022
Amortization Period	30 years
Number of Industrial Properties Collateralizing Mortgage	31
GLA	3,800,000
Property Carrying Value	$ 103,671

Carrying value of industrial properties collateralizing mortgage.

No definition available.

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Namespace Prefix:	fr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt instrument amortization period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Gross Leasable Area

+ References

No definition available.

+ Details

Name:	fr_GrossLeasableArea
Namespace Prefix:	fr_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of industrial properties collateralizing mortgage.

+ References

No definition available.

+ Details

Name:	fr_NumberOfIndustrialPropertiesCollateralizingMortgage
Namespace Prefix:	fr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-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.

+ Details

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

- Definition

Interest rate stated in the contractual debt agreement.

+ References

+ Details

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

- Definition

Date the debt instrument was issued, in CCYY-MM-DD format.

+ References

+ Details

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-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.

+ Details

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Balance Type:	na
Period Type:	duration

- Details

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Balance Type:	na
Period Type:	duration