Organization and Formation of Company - Additional Information (Detail)	Sep. 30, 2012 State Province sqft Jointventures Property
Organization And Formation Of Company [Line Items]
Ownership interest of sole general partner	95.20%
Ownership interest of limited partners	4.80%
Number of industrial properties owned	716
Number of Joint Ventures	2
Number of states in which industrial properties are located	26
Number of provinces in which industrial properties are located	1
Gross Leasable Area (GLA) of industrial properties owned	62,700,000
2007 Europe Joint Venture [Member]
Organization And Formation Of Company [Line Items]
Number of industrial properties owned	0

Noncontrolling interest ownership percentage by parent .

No definition available.

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The number of joint ventures that the entity owns a non-controlling interest in as of the balance sheet date.

No definition available.

The number of provinces in Canada in which the entity operates as of the balance sheet date.

No definition available.

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Namespace Prefix:	fr_
Data Type:	xbrli:integerItemType
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Area of a real estate property.

No definition available.

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Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

No definition available.

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
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Data Type:	num:percentItemType
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Period Type:	instant

The number of real estate properties owned as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
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The number of states the entity operates in as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant