Earnings Per Share / Unit (EPS / EPU) - Computation of Basic and Diluted EPS / EPU (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 40,634	$ 23,803
Net Income Allocable to Participating Securities	(59)	(60)
Net Income Available to Common Stockholders / Unitholders	$ 40,575	$ 23,743
Denominator:
Weighted Average Shares / Units - Basic	126,934	126,194
Performance Units and certain Performance RLP Units (See Note 6)	177	262
Weighted Average Shares / Units - Diluted	127,111	126,456
Basic and Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.32	$ 0.19
First Industrial, L.P.
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 41,479	$ 24,314
Net Income Allocable to Participating Securities	(123)	(76)
Net Income Available to Common Stockholders / Unitholders	$ 41,356	$ 24,238
Denominator:
Weighted Average Shares / Units - Basic	129,070	128,818
Performance Units and certain Performance RLP Units (See Note 6)	330	360
Weighted Average Shares / Units - Diluted	129,400	129,178
Basic and Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.32	$ 0.19