Earnings Per Share (EPS) (Details Textual)	Mar. 31, 2012	Mar. 31, 2011
Earnings Per Share (EPS) (Textual) [Abstract]
Unvested Restricted Stock Awards Outstanding	756,815	696,360

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