Accumulated Other Comprehensive Income (Changes in AOCI) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	$ 1,475,877
Net Current Period Other Comprehensive Income	10,999
Ending Balance	1,663,025
Interest Rate Protection Agreements
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	1,382
Other Comprehensive Income Before Reclassifications	10,470
Amounts Reclassified from Accumulated Other Comprehensive Income	529
Net Current Period Other Comprehensive Income	10,999
Ending Balance	12,381
Comprehensive Income Attributable to Noncontrolling Interest of the Company
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(44)
Other Comprehensive Income Before Reclassifications	(208)
Amounts Reclassified from Accumulated Other Comprehensive Income	0
Net Current Period Other Comprehensive Income	(208)
Ending Balance	(252)
Accumulated Other Comprehensive Income of the Company
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	1,338
Other Comprehensive Income Before Reclassifications	10,262
Amounts Reclassified from Accumulated Other Comprehensive Income	529
Net Current Period Other Comprehensive Income	10,791
Ending Balance	12,129
First Industrial, L.P.
Accumulated Other Comprehensive Income [Line Items]
Net Current Period Other Comprehensive Income	10,999
First Industrial, L.P. | Accumulated Other Comprehensive Income of the Operating Partnership
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	1,382
Other Comprehensive Income Before Reclassifications	10,470
Amounts Reclassified from Accumulated Other Comprehensive Income	529
Net Current Period Other Comprehensive Income	10,999
Ending Balance	$ 12,381