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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 30,911	$ 43,198	$ 112,412	$ 103,469
Net Income Allocable to Participating Securities	(101)	(145)	(349)	(327)
Net Income Available to Common Stockholders / Unitholders	$ 30,810	$ 43,053	$ 112,063	$ 103,142
Denominator:
Weighted Average Shares / Units - Basic	125,768	119,446	123,098	117,870
LTIP Unit Awards (As Defined in Note 9)	362	544	399	482
Weighted Average Shares / Units - Diluted	126,130	119,990	123,497	118,352
Basic Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.24	$ 0.36	$ 0.91	$ 0.88
Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.24	$ 0.36	$ 0.91	$ 0.87
First Industrial, L.P.
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 31,508	$ 44,613	$ 115,333	$ 106,904
Net Income Allocable to Participating Securities	(101)	(145)	(349)	(327)
Net Income Available to Common Stockholders / Unitholders	$ 31,407	$ 44,468	$ 114,984	$ 106,577
Denominator:
Weighted Average Shares / Units - Basic	128,526	123,483	126,380	121,909
LTIP Unit Awards (As Defined in Note 9)	362	544	399	482
Weighted Average Shares / Units - Diluted	128,888	124,027	126,779	122,391
Basic Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.24	$ 0.36	$ 0.91	$ 0.87
Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.24	$ 0.36	$ 0.91	$ 0.87