Condensed Consolidated Statement of Changes in Equity (Unaudited) - USD ($) $ in Thousands	Total	Class A	Class B	Common Stock Class A	Common Stock Class B	Additional Paid-in Capital	Accumulated Earnings (Deficit)	Noncontrolling Interest
Common Stock, Shares, Outstanding, beginning at Sep. 30, 2018				9,112,042	17,213,806
Stockholders' Equity, beginning at Sep. 30, 2018	$ 112,198			$ 1	$ 2	$ 38,562	$ 736	$ 72,897
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-based compensation	951					951
Forfeitures of restricted Class A common stock (shares)				(4,010)
Net income (loss) attributable to i3 Verticals, Inc.	178	$ 178					178
Net loss attributable to non-controlling interests	(2,173)	(2,173)						2,173
Net loss (income)	2,351	$ 2,351
Distributions to non-controlling interest holders	(934)							(934)
Common Stock, Shares, Outstanding, ending at Dec. 31, 2018				9,108,032	17,213,806
Stockholders' Equity, ending at Dec. 31, 2018	114,566			$ 1	$ 2	39,513	914	74,136
Common Stock, Shares, Outstanding, beginning at Sep. 30, 2019		14,444,115	12,921,637	14,444,115	12,921,637
Stockholders' Equity, beginning at Sep. 30, 2019	142,441			$ 1	$ 1	82,380	(2,309)	62,368
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-based compensation	2,124					2,124
Net income (loss) attributable to i3 Verticals, Inc.	(149)	$ (149)					(149)
Net loss attributable to non-controlling interests	(2,083)	(2,083)						2,083
Net loss (income)	$ 1,934	$ 1,934
Exercise of equity-based awards (shares)	103,964			53,662
Exercise of equity-based awards	$ 351					351
Distributions to non-controlling interest holders	0
Common Stock, Shares, Outstanding, ending at Dec. 31, 2019		14,497,777	12,921,637	14,497,777	12,921,637
Stockholders' Equity, ending at Dec. 31, 2019	$ 148,195			$ 1	$ 1	$ 84,855	$ (1,753)	$ 65,091