Quarterly Financial Information (unaudited) - Net Income Available and Basic and Diluted EPS/EPU (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Total Revenues	$ 112,289	$ 116,194	$ 109,202	$ 110,343	$ 110,758	$ 106,590	$ 104,095	$ 104,541	$ 448,028	$ 425,984	$ 403,954
Net Income Available to Common Stockholders / Unitholders and Participating Securities	83,727	35,959	35,669	40,634	96,861	78,311	39,800	23,803	195,989	238,775	163,239
Net Income Allocable to Participating Securities	(137)	(59)	(59)	(59)	(199)	(170)	(89)	(60)	(314)	(518)	(513)
Net Income Available to Common Stockholders / Unitholders	$ 83,590	$ 35,900	$ 35,610	$ 40,575	$ 96,662	$ 78,141	$ 39,711	$ 23,743	$ 195,675	$ 238,257	$ 162,726
Basic and Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders/Unitholders	$ 0.65	$ 0.28	$ 0.28	$ 0.32	$ 0.76	$ 0.62	$ 0.31	$ 0.19	$ 1.53	$ 1.89	$ 1.31
Weighted Average Shares/Units - Basic	128,919	127,903	127,074	126,934	126,682	126,480	126,206	126,194	127,711	126,392	123,804
Weighted Average Shares / Units - Diluted	129,125	128,101	127,266	127,111	127,030	126,783	126,489	126,456	127,904	126,691	124,191
First Industrial, L.P.
Total Revenues	$ 112,289	$ 116,194	$ 109,202	$ 110,343	$ 110,758	$ 106,590	$ 104,095	$ 104,541	$ 448,028	$ 425,984	$ 403,954
Net Income Available to Common Stockholders / Unitholders and Participating Securities	85,484	36,639	36,332	41,479	98,656	79,969	40,689	24,314	199,934	243,628	167,246
Net Income Allocable to Participating Securities	(289)	(125)	(125)	(123)	(279)	(249)	(128)	(76)	(662)	(732)	(513)
Net Income Available to Common Stockholders / Unitholders	$ 85,195	$ 36,514	$ 36,207	$ 41,356	$ 98,377	$ 79,720	$ 40,561	$ 24,238	$ 199,272	$ 242,896	$ 166,733
Basic and Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders/Unitholders	$ 0.65	$ 0.28	$ 0.28	$ 0.32	$ 0.76	$ 0.62	$ 0.31	$ 0.19	$ 1.54	$ 1.89	$ 1.31
Weighted Average Shares/Units - Basic	130,929	129,914	129,081	129,070	128,837	128,837	128,831	128,818	129,752	128,831	126,921
Weighted Average Shares / Units - Diluted	131,339	130,294	129,461	129,400	129,308	129,256	129,221	129,178	130,127	129,241	127,308