Earnings Per Share / Unit (EPS / EPU) - Computation of Basic and Diluted EPS / EPU (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 36,292	$ 22,709
Net Income Allocable to Participating Securities	(97)	(67)
Net Income Available to Common Stockholders / Unitholders	$ 36,195	$ 22,642
Denominator:
Weighted Average Shares / Units - Basic	119,846	116,837
LTIP Unit Awards (As Defined in Note 9)	365	424
Weighted Average Shares / Units - Diluted	120,211	117,261
Basic and Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.30	$ 0.19
First Industrial, L.P.
Numerator:
Net Income Available to Common Stockholders / Unitholders and Participating Securities	$ 37,443	$ 23,464
Net Income Allocable to Participating Securities	(97)	(66)
Net Income Available to Common Stockholders / Unitholders	$ 37,346	$ 23,398
Denominator:
Weighted Average Shares / Units - Basic	123,729	120,877
LTIP Unit Awards (As Defined in Note 9)	365	424
Weighted Average Shares / Units - Diluted	124,094	121,301
Basic and Diluted Earnings Per Share / Unit:
Net Income Available to Common Stockholders / Unitholders	$ 0.30	$ 0.19

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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Amount of earnings (loss) distributed and earnings (loss) allocated to participating securities for the basic earnings (loss) per share or per unit calculation under the two-class method.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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