CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income		$ 200,169	$ 243,881	$ 167,334
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Depreciation		102,533	98,333	94,626
Amortization of Debt Issuance Costs		3,428	3,218	3,404
Other Amortization, including Stock Based Compensation		35,231	28,780	26,976
Impairment of Real Estate		0	0	2,756
Provision for Bad Debt		0	0	350
Equity in (Income) Loss of Joint Ventures		(4,200)	(16,235)	276
Distributions from Joint Ventures		4,279	15,959	0
Gain on Sale of Real Estate	[1]	(86,751)	(124,942)	(81,600)
Loss from Retirement of Debt		0	0	39
Gain on Casualty and Involuntary Conversion		(6,476)	0	(392)
Payments to Settle Derivative Instruments		0	(3,149)	0
Straight-line Rental Income and Expense, Net		(8,973)	(10,884)	(2,165)
Decrease (Increase) in Tenant Accounts Receivable, Prepaid Expenses and Other Assets, Net and Operating Lease Right-of-Use Assets		3,861	(11,523)	(4,199)
(Decrease) Increase in Accounts Payable, Accrued Expenses, Other Liabilities, Rents Received in Advance and Security Deposits		(2,671)	22,095	3,090
Net Cash Provided by Operating Activities		240,430	245,533	210,495
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions of Real Estate		(220,223)	(152,744)	(157,787)
Additions to Investment in Real Estate and Non-Acquisition Tenant Improvements and Lease Costs		(198,496)	(294,633)	(224,466)
Net Proceeds from Sales of Investments in Real Estate, Including Sales-Type Lease Receivable		203,864	254,416	184,783
Increase in Escrow Deposits		(14,950)	(23,113)	(1,326)
Proceeds from Casualty and Involuntary Conversion		6,476	0	906
Contributions to and Investments in Joint Venture		(42,744)	(210)	(25,190)
Distributions from Joint Venture		19,938	8,711	1,829
Other Investing Activity		(5,603)	2,187	(2,147)
Net Cash Used in Investing Activities		(251,738)	(205,386)	(223,398)
CASH FLOWS FROM FINANCING ACTIVITIES:
Financing and Equity Issuance Costs		(3,363)	(954)	(2,975)
Proceeds from the Issuance of Common Stock/Contribution of General Partner Units		78,718	0	145,584
Tax Paid on Shares Withheld		(5,944)	(4,384)	(6,020)
Common Stock Dividends and Unit Distributions Paid		(127,338)	(117,214)	(109,649)
Contributions from Noncontrolling Interests		4,321	0	0
Repayments on Mortgage Loans Payable		(30,146)	(123,250)	(165,646)
Proceeds from Senior Unsecured Notes		300,000	150,000	300,000
Proceeds from Unsecured Credit Facility		247,000	415,000	237,000
Repayments on Unsecured Credit Facility		(405,000)	(257,000)	(381,500)
Net Cash Provided by Financing Activities		58,248	62,198	16,794
Net Increase in Cash, Cash Equivalents and Restricted Cash		46,940	102,345	3,891
Cash, Cash Equivalents and Restricted Cash, Beginning of Year		152,718	50,373	46,482
Cash, Cash Equivalents and Restricted Cash, End of Year		199,658	152,718	50,373
SUPPLEMENTAL INFORMATION TO STATEMENTS OF CASH FLOWS:
Interest Paid, Net of Interest Expense Capitalized in Connection with Development Activity		48,849	47,801	47,408
Interest Expense Capitalized in Connection with Development Activity		6,847	5,757	5,869
Income Taxes Paid		1,573	3,583	457
Cash Paid for Operating Lease Liabilities		2,821	2,084	0
Supplemental Schedule of Non-Cash Operating Activities:
Operating Lease Liabilities Arising from Obtaining Right-of-Use Assets		1,341	22,871	0
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Dividends and Distributions Payable		33,703	30,567	28,845
Exchange of Limited Partner Units for Common Stock/General Partner Units
Conversion of Limited Partner Units to Common Stock / General Partner Units		0	0	0
Lease Reclassification from Operating Lease to Sales-Type Lease:
Land		(1,087,907)	(957,478)
Deferred Rent Receivables, Net		(84,567)	(77,703)
Assumption of Indebtedness and Other Liabilities in Connection with the Acquisition of Real Estate		18,579	1,466	11,878
Accounts Payable Related to Construction in Progress and Additions to Investment in Real Estate		34,008	51,107	31,545
Write-off of Fully Depreciated Assets		(45,302)	(37,892)	(43,654)
Sales Type Lease
Lease Reclassification from Operating Lease to Sales-Type Lease:
Sales-type Lease, Lease Receivable		0	54,521	0
Land		0	(24,803)	0
Building Net Of Accumulated Depreciation		0	(17,845)	0
Deferred Rent Receivables, Net		0	(2,073)	0
Other Assets Net Of Accumulated Amortization		0	(1,194)	0
Sales-type Lease, Selling Profit (Loss)		0	8,606	0
Noncontrolling Interests
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income		4,180	5,106	4,095
Exchange of Limited Partner Units for Common Stock/General Partner Units
Conversion of Limited Partner Units to Common Stock / General Partner Units		(2,090)	(7,196)	(16,605)
Common Stock
Exchange of Limited Partner Units for Common Stock/General Partner Units
Conversion of Limited Partner Units to Common Stock / General Partner Units		2	5	13
Additional Paid-in- Capital
Exchange of Limited Partner Units for Common Stock/General Partner Units
Conversion of Limited Partner Units to Common Stock / General Partner Units		2,088	7,191	16,592
First Industrial, L.P.
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income		200,169	243,881	167,334
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Depreciation		102,533	98,333	94,626
Amortization of Debt Issuance Costs		3,428	3,218	3,404
Other Amortization, including Stock Based Compensation		35,231	28,780	26,976
Impairment of Real Estate		0	0	2,756
Provision for Bad Debt		0	0	350
Equity in (Income) Loss of Joint Ventures		(4,200)	(16,235)	276
Distributions from Joint Ventures		4,279	15,959	0
Gain on Sale of Real Estate		(86,751)	(124,942)	(81,600)
Loss from Retirement of Debt		0	0	39
Gain on Casualty and Involuntary Conversion		(6,476)	0	(392)
Payments to Settle Derivative Instruments		0	(3,149)	0
Straight-line Rental Income and Expense, Net		(8,973)	(10,884)	(2,165)
Decrease (Increase) in Tenant Accounts Receivable, Prepaid Expenses and Other Assets, Net and Operating Lease Right-of-Use Assets		4,512	(11,436)	(4,189)
(Decrease) Increase in Accounts Payable, Accrued Expenses, Other Liabilities, Rents Received in Advance and Security Deposits		(2,671)	22,095	3,090
Net Cash Provided by Operating Activities		241,081	245,620	210,505
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions of Real Estate		(220,223)	(152,744)	(157,787)
Additions to Investment in Real Estate and Non-Acquisition Tenant Improvements and Lease Costs		(198,496)	(294,633)	(224,466)
Net Proceeds from Sales of Investments in Real Estate, Including Sales-Type Lease Receivable		203,864	254,416	184,783
Increase in Escrow Deposits		(14,950)	(23,113)	(1,326)
Proceeds from Casualty and Involuntary Conversion		6,476	0	906
Contributions to and Investments in Joint Venture		(42,744)	(210)	(25,190)
Distributions from Joint Venture		19,938	8,711	1,829
Other Investing Activity		(5,603)	2,187	(2,147)
Net Cash Used in Investing Activities		(251,738)	(205,386)	(223,398)
CASH FLOWS FROM FINANCING ACTIVITIES:
Financing and Equity Issuance Costs		(3,363)	(954)	(2,975)
Proceeds from the Issuance of Common Stock/Contribution of General Partner Units		78,718	0	145,584
Tax Paid on Shares Withheld		(5,944)	(4,384)	(6,020)
Common Stock Dividends and Unit Distributions Paid		(127,338)	(117,214)	(109,649)
Contributions from Noncontrolling Interests		4,401	32	126
Distributions to Noncontrolling Interests		(731)	(119)	(136)
Repayments on Mortgage Loans Payable		(30,146)	(123,250)	(165,646)
Proceeds from Senior Unsecured Notes		300,000	150,000	300,000
Proceeds from Unsecured Credit Facility		247,000	415,000	237,000
Repayments on Unsecured Credit Facility		(405,000)	(257,000)	(381,500)
Net Cash Provided by Financing Activities		57,597	62,111	16,784
Net Increase in Cash, Cash Equivalents and Restricted Cash		46,940	102,345	3,891
Cash, Cash Equivalents and Restricted Cash, Beginning of Year		152,718	50,373	46,482
Cash, Cash Equivalents and Restricted Cash, End of Year		199,658	152,718	50,373
SUPPLEMENTAL INFORMATION TO STATEMENTS OF CASH FLOWS:
Interest Paid, Net of Interest Expense Capitalized in Connection with Development Activity		48,849	47,801	47,408
Interest Expense Capitalized in Connection with Development Activity		6,847	5,757	5,869
Income Taxes Paid		1,573	3,583	457
Cash Paid for Operating Lease Liabilities		2,821	2,084	0
Supplemental Schedule of Non-Cash Operating Activities:
Operating Lease Liabilities Arising from Obtaining Right-of-Use Assets		1,341	22,871	0
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Dividends and Distributions Payable		33,703	30,567	28,845
Exchange of Limited Partner Units for Common Stock/General Partner Units
Conversion of Limited Partner Units to Common Stock / General Partner Units		0	0	0
Lease Reclassification from Operating Lease to Sales-Type Lease:
Land		(1,087,907)	(957,478)
Deferred Rent Receivables, Net		(84,567)	(77,703)
Assumption of Indebtedness and Other Liabilities in Connection with the Acquisition of Real Estate		18,579	1,466	11,878
Accounts Payable Related to Construction in Progress and Additions to Investment in Real Estate		34,008	51,107	31,545
Write-off of Fully Depreciated Assets		(45,302)	(37,892)	(43,654)
First Industrial, L.P. | Sales Type Lease
Lease Reclassification from Operating Lease to Sales-Type Lease:
Sales-type Lease, Lease Receivable		0	54,521	0
Land		0	(24,803)	0
Building Net Of Accumulated Depreciation		0	(17,845)	0
Deferred Rent Receivables, Net		0	(2,073)	0
Other Assets Net Of Accumulated Amortization		0	(1,194)	0
Sales-type Lease, Selling Profit (Loss)		0	8,606	0
First Industrial, L.P. | Limited Partner Units
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income		4,189	5,106	4,095
Exchange of Limited Partner Units for Common Stock/General Partner Units
Conversion of Limited Partner Units to Common Stock / General Partner Units		(2,090)	(7,196)	(16,605)
First Industrial, L.P. | General Partner Units
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income		195,745	238,522	163,151
Exchange of Limited Partner Units for Common Stock/General Partner Units
Conversion of Limited Partner Units to Common Stock / General Partner Units		$ 2,090	$ 7,196	$ 16,605

[1] (B) Gross proceeds and gain on sale of real estate include the sale of several land parcels for the years ended December 31, 2019 and 2018. In addition, included in the above table for the year ended December 31, 2019, is 0.6 million square feet of GLA, gross proceeds of $54,521 and gain on sale of $8,606 related to the reclassification of a lease from an operating lease to a sales-type lease that was recorded as a lease receivable as of December 31, 2019 and collected during 2020. See Note 10 for additional information.