Earnings Per Share (EPS) (Details Textual) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share (EPS) (Textual) [Abstract]
Unvested Restricted Stock Awards Outstanding	673,381	662,092	355,645

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