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Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Jun. 25, 2018
Class of Stock [Line Items]
Provision for income taxes	$ 149	$ 265
Percent of tax benefits payable to continuing equity owners			85.00%
Tax benefits retained (percent)			15.00%
Common units of i3 Verticals, LLC redeemed during the period	0
Period of payment to Continuing Equity Owners	24 years
Minimum
Class of Stock [Line Items]
Expected payments to Continuing Equity Owners related to exchange of common units	$ 0
Maximum
Class of Stock [Line Items]
Expected payments to Continuing Equity Owners related to exchange of common units	2,103
Continuing Equity Owner \| Class B Common Stock
Class of Stock [Line Items]
Deferred tax asset recognized	26,736
Tax benefits due to Continuing Equity Owners	$ 23,229