Accumulated Other Comprehensive Income (Changes in AOCI) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	$ 1,475,877
Net Current Period Other Comprehensive Income	9,297
Ending Balance	1,655,812
Interest Rate Protection Agreements
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	1,382
Other Comprehensive Income Before Reclassifications	8,690
Amounts Reclassified from Accumulated Other Comprehensive Income	607
Net Current Period Other Comprehensive Income	9,297
Ending Balance	10,679
Comprehensive Income Attributable to Noncontrolling Interest of the Company
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(44)
Other Comprehensive Income Before Reclassifications	(200)
Amounts Reclassified from Accumulated Other Comprehensive Income	0
Net Current Period Other Comprehensive Income	(200)
Ending Balance	(244)
Accumulated Other Comprehensive Income of the Company
Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	1,338
Other Comprehensive Income Before Reclassifications	8,490
Amounts Reclassified from Accumulated Other Comprehensive Income	607
Net Current Period Other Comprehensive Income	9,097
Ending Balance	10,435
First Industrial, L.P.
Accumulated Other Comprehensive Income [Line Items]
Net Current Period Other Comprehensive Income	9,297
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	8,690
Amounts Reclassified from Accumulated Other Comprehensive Income	607
Net Current Period Other Comprehensive Income	9,297
Ending Balance	$ 10,679