Accumulated Other Comprehensive Income (Changes in AOCI) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($)
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	$ 1,798,263
Ending Balance	1,888,599
Derivative Instruments
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(7,013)
Other Comprehensive Loss Before Reclassifications	(18,222)
Amounts Reclassified from Accumulated Other Comprehensive Loss	4,847
Net Current Period Other Comprehensive Loss	(13,375)
Ending Balance	(20,388)
Comprehensive Loss Attributable to Noncontrolling Interest of the Company
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	130
Other Comprehensive Loss Before Reclassifications	289
Amounts Reclassified from Accumulated Other Comprehensive Loss	0
Net Current Period Other Comprehensive Loss	289
Ending Balance	419
Accumulated Other Comprehensive Loss of the Company
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(6,883)
Other Comprehensive Loss Before Reclassifications	(17,933)
Amounts Reclassified from Accumulated Other Comprehensive Loss	4,847
Net Current Period Other Comprehensive Loss	(13,086)
Ending Balance	(19,969)
First Industrial, L.P. | Accumulated Other Comprehensive Loss of the Operating Partnership
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(7,013)
Other Comprehensive Loss Before Reclassifications	(18,222)
Amounts Reclassified from Accumulated Other Comprehensive Loss	4,847
Net Current Period Other Comprehensive Loss	(13,375)
Ending Balance	$ (20,388)