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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 45,209	$ 37,562	$ 81,501	$ 60,271
Net Income Allocable to Participating Securities	(151)	(129)	(248)	(196)
Net Income Available to Common Stockholders / Unitholders	$ 45,058	$ 37,433	$ 81,253	$ 60,075
Denominator:
Weighted Average Shares / Units - Basic	123,616	117,299	121,741	117,070
LTIP Unit Awards (As Defined in Note 9)	469	480	417	452
Weighted Average Shares / Units - Diluted	124,085	117,779	122,158	117,522
Basic and Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.36	$ 0.32	$ 0.67	$ 0.51
First Industrial, L.P.
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 46,382	$ 38,827	$ 83,825	$ 62,291
Net Income Allocable to Participating Securities	(151)	(129)	(248)	(196)
Net Income Available to Common Stockholders / Unitholders	$ 46,231	$ 38,698	$ 83,577	$ 62,095
Denominator:
Weighted Average Shares / Units - Basic	126,832	121,339	125,289	121,109
LTIP Unit Awards (As Defined in Note 9)	469	480	417	452
Weighted Average Shares / Units - Diluted	127,301	121,819	125,706	121,561
Basic and Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.36	$ 0.32	$ 0.67	$ 0.51