Nature of Operations and Summary of Significant Accounting Policies - Narrative (Details) $ / shares in Units, check_deposit in Billions	3 Months Ended				9 Months Ended
	Jun. 30, 2021 USD ($) patent institution check_deposit $ / shares	Sep. 30, 2020 USD ($) $ / shares	Jun. 30, 2020 USD ($)		Jun. 30, 2021 USD ($) segment patent institution check_deposit $ / shares	Jun. 30, 2020 USD ($)		Feb. 05, 2021 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of financial institutions signed agreements to deploy mobile deposit (more than) | institution	7,500				7,500
Number of check deposits processed (over five billion) | check_deposit	5				5
Number of patents granted | patent	73				73
Number of pending patent applications | patent	15				15
Net gains resulting from foreign exchange translation	$ 747,000		$ 1,135,000		$ 859,000	$ 1,324,000
Product management costs	6,946,000		5,891,000	[1]	19,801,000	16,764,000	[1]
Other than temporary impairment charges recognized on investments	$ 0		0		$ 0	0
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001			$ 0.001
Write-offs of allowance for doubtful accounts	$ 35,000				$ 100,000
Allowance for doubtful accounts receivable	300,000	$ 200,000			300,000
Capitalized software development costs	0		0		0	0
Amortization expense of capitalized software development costs	0		0		0	0
Capitalized software development costs for internal use					600,000	100,000
Amortization expense from capitalized software development costs for internal use					$ 300,000	300,000
Number of operating segments | segment					1
Number of reporting units | segment					1
Goodwill impairment		0
Impairment charges related to intangible assets	0		0		$ 0	0
Trading-day average stock price period					20 days
Accumulated other comprehensive income (loss)	$ 361,000	(323,000)			$ 361,000
Convertible Debt | 2026 Notes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt issued								$ 155,300,000
Debt interest rate								0.75%
Revision of Prior Period, Reclassification, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product management costs			$ 800,000			$ 2,200,000
ICAR | Spanish Government Agencies
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt interest rate	0.00%				0.00%
Amount outstanding under loan agreement	$ 900,000	700,000			$ 900,000
ICAR | Spanish Government Agencies | Other current liabilities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Amount outstanding under loan agreement	100,000	100,000			100,000
ICAR | Spanish Government Agencies | Other non-current liabilities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Amount outstanding under loan agreement	$ 800,000	$ 600,000			$ 800,000
Minimum | ICAR | Spanish Government Agencies
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of loan agreement					5 years
Maximum | ICAR | Spanish Government Agencies
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Term of loan agreement					12 years

[1] June 30, 2020 consolidated statements of operations reflect reclassifications to conform to the current year presentation.