Nature of Operations and Summary of Significant Accounting Policies - Additional Information (Details) $ / shares in Units, check_deposit in Billions		3 Months Ended	12 Months Ended
	Oct. 01, 2019 USD ($)	Sep. 30, 2020 USD ($) patent institution check_deposit $ / shares	Sep. 30, 2020 USD ($) patent institution check_deposit segment $ / shares	Sep. 30, 2019 USD ($) $ / shares		Sep. 30, 2018 USD ($)
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of financial services organizations, leading marketplace and financial technology brands (more than) | institution		7,500	7,500
Number of check deposits processed (over) | check_deposit		4	4
Number of patents granted | patent		67	67
Number of patent applications pending | patent		20	20
Foreign currency translation gains (losses)			$ 3,635,000	$ (3,504,000)		$ (723,000)
Product management costs			22,859,000	21,873,000	[1]	18,118,000	[1]
Other-than-temporary impairment charges recognized in earnings			0	0		0
Write-offs of allowance for doubtful accounts			200,000	100,000		0
Allowance for doubtful accounts receivable		$ 200,000	200,000	200,000
Depreciation and amortization of property and equipment			1,504,000	1,388,000		615,000
Repairs and maintenance expenses			100,000	100,000		100,000
Impairment or long-lived assets			0	0		0
Capitalized software development costs		0	0	0
Amortization expense for capitalized software development costs			0	0		0
Capitalized software development costs for internal use		300,000	300,000	200,000		900,000
Amortization expense for capitalized software development costs for internal use			$ 400,000	$ 300,000		100,000
Number of operating segments | segment			1
Number of reporting units | segment			1
Goodwill impairment		$ 0
Preferred stock, par value (in dollars per share) | $ / shares		$ 0.001	$ 0.001	$ 0.001
Impairment to intangible assets			$ 0	$ 0		0
Trading-day average stock price period			20 days
Advertising costs			$ 1,600,000	800,000		$ 500,000
Accumulated other comprehensive loss		$ 323,000	323,000	$ 4,061,000
Operating lease liabilities	$ 8,200,000	7,146,000	7,146,000
Operating ROU assets	$ 6,800,000	$ 5,407,000	5,407,000
Accounting Standard Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member			us-gaap:AccountingStandardsUpdate201409Member		us-gaap:AccountingStandardsUpdate201609Member
Revision of Prior Period, Reclassification, Adjustment
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Product management costs			$ 3,000,000.0	$ 2,900,000		$ 2,400,000
ICAR | Spanish Government Agencies
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Interest rate of loan agreements		0.00%	0.00%
Total amounts outstanding under loan agreements		$ 700,000	$ 700,000	600,000
ICAR | Spanish Government Agencies | Other Current Liabilities
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Current amount outstanding under loan agreements		100,000	100,000	200,000
ICAR | Spanish Government Agencies | Other Noncurrent Liabilities
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Non-current amount outstanding under loan agreements		$ 600,000	$ 600,000	$ 400,000
Minimum
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives			3 years
Minimum | ICAR | Spanish Government Agencies
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Repayment period of loan agreements			5 years
Maximum
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives			10 years
Maximum | ICAR | Spanish Government Agencies
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Repayment period of loan agreements			12 years

[1] September 30, 2019 and 2018 consolidated statements of operations reflect reclassifications to conform to the current year presentation.