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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 96,861	$ 78,311	$ 39,800	$ 23,803	$ 50,827	$ 30,911	$ 45,209	$ 36,292	$ 238,775	$ 163,239	$ 201,456
Net Income Allocable to Participating Securities	(199)	(170)	(89)	(60)	(164)	(101)	(151)	(97)	(518)	(513)	(646)
Net Income Available to Common Stockholders / Unitholders	$ 96,662	$ 78,141	$ 39,711	$ 23,743	$ 50,663	$ 30,810	$ 45,058	$ 36,195	$ 238,257	$ 162,726	$ 200,810
Denominator:
Weighted Average Shares/Units - Basic	126,682	126,480	126,206	126,194	125,897	125,768	123,616	119,846	126,392	123,804	118,272
LTIP Unit Awards (As Defined in Note 11)									299	387	515
Weighted Average Shares / Units - Diluted	127,030	126,783	126,489	126,456	126,249	126,130	124,085	120,211	126,691	124,191	118,787
Basic Earnings Per Share / Unit:
Net Income Available to Common Stockholders/Unitholders	$ 0.76	$ 0.62	$ 0.31	$ 0.19	$ 0.40	$ 0.24	$ 0.36	$ 0.30	$ 1.89	$ 1.31	$ 1.70
Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders/Unitholders	$ 0.76	$ 0.62	$ 0.31	$ 0.19	$ 0.40	$ 0.24	$ 0.36	$ 0.30	$ 1.88	$ 1.31	$ 1.69
First Industrial, L.P.
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 98,656	$ 79,969	$ 40,689	$ 24,314	$ 51,913	$ 31,508	$ 46,382	$ 37,443	$ 243,628	$ 167,246	$ 208,158
Net Income Allocable to Participating Securities	(279)	(249)	(128)	(76)	(164)	(101)	(151)	(97)	(732)	(513)	(646)
Net Income Available to Common Stockholders / Unitholders	$ 98,377	$ 79,720	$ 40,561	$ 24,238	$ 51,749	$ 31,407	$ 46,231	$ 37,346	$ 242,896	$ 166,733	$ 207,512
Denominator:
Weighted Average Shares/Units - Basic	128,837	128,837	128,831	128,818	128,526	128,526	126,832	123,729	128,831	126,921	122,306
LTIP Unit Awards (As Defined in Note 11)									410	387	515
Weighted Average Shares / Units - Diluted	129,308	129,256	129,221	129,178	128,878	128,888	127,301	124,094	129,241	127,308	122,821
Basic Earnings Per Share / Unit:
Net Income Available to Common Stockholders/Unitholders	$ 0.76	$ 0.62	$ 0.31	$ 0.19	$ 0.40	$ 0.24	$ 0.36	$ 0.30	$ 1.89	$ 1.31	$ 1.70
Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders/Unitholders	$ 0.76	$ 0.62	$ 0.31	$ 0.19	$ 0.40	$ 0.24	$ 0.36	$ 0.30	$ 1.88	$ 1.31	$ 1.69