Earnings Per Share (EPS) - Additional Information (Detail)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Unvested restricted stock awards outstanding	463,774	488,861	288,627

Number of unvested restricted stock awards outstanding included in participating securities.

No definition available.

Name:	fr_NumberOfUnvestedRestrictedStockAwardsOutstandingIncludedInParticipatingSecurities
Namespace Prefix:	fr_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant