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, 2021	Mar. 31, 2020
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 62,198	$ 40,634
Net Income Allocable to Participating Securities	(61)	(59)
Net Income Available to Common Stockholders / Unitholders	$ 62,137	$ 40,575
Denominator:
Weighted Average Shares / Units - Basic	129,088	126,934
Performance Units (See Note 9) / Performance Units and certain Performance RLP Units (See Note 6)	84	177
Weighted Average Shares / Units - Diluted	129,172	127,111
Basic and Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.48	$ 0.32
First Industrial, L.P.
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 63,565	$ 41,479
Net Income Allocable to Participating Securities	(160)	(123)
Net Income Available to Common Stockholders / Unitholders	$ 63,405	$ 41,356
Denominator:
Weighted Average Shares / Units - Basic	131,172	129,070
Performance Units (See Note 9) / Performance Units and certain Performance RLP Units (See Note 6)	462	330
Weighted Average Shares / Units - Diluted	131,634	129,400
Basic and Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.48	$ 0.32