Summary of Significant Accounting Policies (Details)			12 Months Ended
		Oct. 01, 2020 USD ($)	Sep. 30, 2021 USD ($) reportable_unit	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Oct. 01, 2019 USD ($)	Sep. 30, 2018 USD ($)
Concentration Risk [Line Items]
Allowance for doubtful accounts			$ 181,000	$ 310,000
Settlement assets			4,768,000	0
Settlement obligations			4,768,000	0
Inventory			2,220,000	1,309,000
Impairment charges			$ 0	0	$ 0
Estimated useful life			3 years
Notes receivable, fair value disclosure			$ 4,695,000	1,195,000
Revenue from acquisitions			57,819,000
Net income			6,530,000
Goodwill impairment			$ 0	0	0
Number of reporting units | reportable_unit			5
Amortization expense of intangible assets			$ 15,830,000	12,414,000	12,394,000
Impairment of intangible assets, excluding goodwill			0	0	0
Contract with customer, asset, before allowance for credit loss			1,505,000,000	0
Capitalized contract cost, gross			3,851,000	3,140,000
Advertising expense			2,623,000	1,813,000	1,443,000
Equity-based compensation expense			20,860,000	10,452,000	6,124,000
Benefit from income taxes			(623,000)	2,795,000	177,000
Cumulative increase to equity			289,591,000	240,168,000	142,441,000		$ 112,198,000
Cumulative increase to accumulated earnings			(6,480,000)	(2,023,000)
Cumulative increase to non-controlling interest			84,831,000	84,590,000
Interchange and network fees	[1]		0	0	242,867,000
Operating lease right-of-use assets			14,479,000	0
Operating lease liabilities, less current portion			11,960,000
Increase (decrease) in prepaid expense and other assets		$ 202,000	1,564,000	984,000	817,000
Accrued expenses and other current liabilities		869,000	10,453,000	1,575,000	1,572,000
Operating Expense
Concentration Risk [Line Items]
Interchange and network fees				244,097,000	242,867,000
Cumulative Effect, Period of Adoption, Adjustment
Concentration Risk [Line Items]
Cumulative increase to equity					1,345,000	$ 1,345,000
Cumulative increase to accumulated earnings						705,000
Cumulative increase to non-controlling interest						$ 640,000
Operating lease right-of-use assets		9,093,000
Operating lease liabilities, less current portion		$ 9,760,000
Class B Common Stock
Concentration Risk [Line Items]
Reduction in the benefit from income taxes				235,000
Increase to net loss				3,728,000
Reduction in company's net loss				3,493,000
Intangible Assets, Amortization Period
Concentration Risk [Line Items]
Amortization expense of intangible assets			$ 533,000	398,000	$ 1,290,000
Change in Accounting Method Accounted for as Change in Estimate
Concentration Risk [Line Items]
Change in valuation allowance for deferred tax assets				2,668,000
Benefit from income taxes				$ (2,668,000)

[1] Effective October 1, 2019, the Company's revenues are presented net of interchange and network fees in accordance with Accounting Standards Codification Topic 606, Revenue from Contracts with Customers. See Note 2 to our consolidated financial statements for a description of the recently adopted accounting pronouncement.