Accumulated Other Comprehensive Income (Changes in AOCI) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	$ 1,947,320
Ending Balance	1,980,885
Derivative Instruments
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(17,308)
Other Comprehensive Gain Before Reclassifications	4,956
Amounts Reclassified from Accumulated Other Comprehensive Loss	1,799
Net Current Period Other Comprehensive Gain	6,755
Ending Balance	(10,553)
Comprehensive Loss Attributable to Noncontrolling Interest of the Company
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	355
Other Comprehensive Gain Before Reclassifications	(114)
Amounts Reclassified from Accumulated Other Comprehensive Loss	0
Net Current Period Other Comprehensive Gain	(114)
Ending Balance	241
Accumulated Other Comprehensive Loss of the Company
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(16,953)
Other Comprehensive Gain Before Reclassifications	4,842
Amounts Reclassified from Accumulated Other Comprehensive Loss	1,799
Net Current Period Other Comprehensive Gain	6,641
Ending Balance	(10,312)
First Industrial, L.P. | Accumulated Other Comprehensive Loss of the Operating Partnership
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(17,308)
Other Comprehensive Gain Before Reclassifications	4,956
Amounts Reclassified from Accumulated Other Comprehensive Loss	1,799
Net Current Period Other Comprehensive Gain	6,755
Ending Balance	$ (10,553)