Accumulated Other Comprehensive Income (Changes in AOCI) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 1,798,263	$ 1,679,911
Ending Balance	1,947,320	1,798,263
Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(7,013)	3,574
Other Comprehensive Loss Before Reclassifications	(17,422)	(9,603)
Amounts Reclassified from Accumulated Other Comprehensive Income	7,127	(984)
Net Current Period Other Comprehensive Loss	(10,295)	(10,587)
Ending Balance	(17,308)	(7,013)
Comprehensive Income (Loss) Attributable to Noncontrolling Interest of the Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	130	(72)
Other Comprehensive Loss Before Reclassifications	225	202
Amounts Reclassified from Accumulated Other Comprehensive Income	0	0
Net Current Period Other Comprehensive Loss	225	202
Ending Balance	355	130
Accumulated Other Comprehensive Income (Loss) of the Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6,883)	3,502
Other Comprehensive Loss Before Reclassifications	(17,197)	(9,401)
Amounts Reclassified from Accumulated Other Comprehensive Income	7,127	(984)
Net Current Period Other Comprehensive Loss	(10,070)	(10,385)
Ending Balance	(16,953)	(6,883)
First Industrial, L.P. | Accumulated Other Comprehensive Income of the Operating Partnership
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(7,013)	3,574
Other Comprehensive Loss Before Reclassifications	(17,422)	(9,603)
Amounts Reclassified from Accumulated Other Comprehensive Income	7,127	(984)
Net Current Period Other Comprehensive Loss	(10,295)	(10,587)
Ending Balance	$ (17,308)	$ (7,013)