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								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 50,827	$ 30,911	$ 45,209	$ 36,292	$ 97,987	$ 43,198	$ 37,562	$ 22,709	$ 163,239	$ 201,456	$ 121,232
Net Income Allocable to Participating Securities	(164)	(101)	(151)	(97)	(331)	(145)	(129)	(67)	(513)	(646)	(411)
Net Income Available to Common Stockholders / Unitholders	$ 50,663	$ 30,810	$ 45,058	$ 36,195	$ 97,656	$ 43,053	$ 37,433	$ 22,642	$ 162,726	$ 200,810	$ 120,821
Denominator:
Weighted Average Shares/Units - Basic	125,897	125,768	123,616	119,846	119,462	119,446	117,299	116,837	123,804	118,272	115,030
LTIP Unit Awards (As Defined in Note 11)									387	515	340
Weighted Average Shares / Units - Diluted	126,249	126,130	124,085	120,211	120,076	119,990	117,779	117,261	124,191	118,787	115,370
Basic Earnings Per Share / Unit:
Net Income Available to Common Stockholders/Unitholders	$ 0.40	$ 0.24	$ 0.36	$ 0.30	$ 0.82	$ 0.36	$ 0.32	$ 0.19	$ 1.31	$ 1.70	$ 1.05
Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders/Unitholders	$ 0.40	$ 0.24	$ 0.36	$ 0.30	$ 0.81	$ 0.36	$ 0.32	$ 0.19	$ 1.31	$ 1.69	$ 1.05
First Industrial, L.P.
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 51,913	$ 31,508	$ 46,382	$ 37,443	$ 101,254	$ 44,613	$ 38,827	$ 23,464	$ 167,246	$ 208,158	$ 125,547
Net Income Allocable to Participating Securities	(164)	(101)	(151)	(97)	(331)	(145)	(129)	(66)	(513)	(646)	(410)
Net Income Available to Common Stockholders / Unitholders	$ 51,749	$ 31,407	$ 46,231	$ 37,346	$ 100,923	$ 44,468	$ 38,698	$ 23,398	$ 166,733	$ 207,512	$ 125,137
Denominator:
Weighted Average Shares/Units - Basic	128,526	128,526	126,832	123,729	123,483	123,483	121,339	120,877	126,921	122,306	119,274
LTIP Unit Awards (As Defined in Note 11)									387	515	340
Weighted Average Shares / Units - Diluted	128,878	128,888	127,301	124,094	124,097	124,027	121,819	121,301	127,308	122,821	119,614
Basic Earnings Per Share / Unit:
Net Income Available to Common Stockholders/Unitholders	$ 0.40	$ 0.24	$ 0.36	$ 0.30	$ 0.82	$ 0.36	$ 0.32	$ 0.19	$ 1.31	$ 1.70	$ 1.05
Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders/Unitholders	$ 0.40	$ 0.24	$ 0.36	$ 0.30	$ 0.81	$ 0.36	$ 0.32	$ 0.19	$ 1.31	$ 1.69	$ 1.05