STOCKHOLDERS’ EQUITY - Narrative (Details) - USD ($)	3 Months Ended
STOCKHOLDERS’ EQUITY - Narrative (Details) - USD ($)	Dec. 31, 2025	Dec. 31, 2024	Sep. 30, 2025	May 13, 2024	Oct. 02, 2023	Jan. 31, 2020	Mar. 07, 2018	Mar. 10, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to outstanding stock options and RSUs	$ 46,000,000.0
Weighted average period for unrecognized compensation expense expected to be recognized (in years)	2 years 8 months 12 days
Purchase of common stock (in shares)	153,389		158,589
Recognized compensation expense	$ 2,691,000	$ 4,465,000
Options granted (in shares)	0	0
Amount authorized and approved under share repurchase program				$ 50,000,000.0
Amount of shares repurchased	$ 10,000,000.0	$ 3,300,000
Number of shares repurchased (in shares)	1,078,333	363,378
Average price of shares repurchased (in dollars per share)	$ 9.27	$ 8.99
Share repurchase program, share purchased amount	$ 39,000,000.0
Inducement Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase of common stock (in shares)	45,000
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for unrecognized compensation expense expected to be recognized (in years)	3 years
Awards outstanding (in shares)	3,425,644		2,926,842
Recognized compensation expense	$ 1,700,000	$ 2,900,000
Unrecognized compensation expense related to nonvested awards	$ 26,000,000.0
RSUs \| Inducement Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)	260,763
Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for unrecognized compensation expense expected to be recognized (in years)	2 years 2 months 12 days
Awards outstanding (in shares)	2,356,495		2,022,284
Recognized compensation expense	$ 900,000	1,400,000
Unrecognized compensation expense related to nonvested awards	$ 19,900,000
Performance RSUs \| Inducement Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)	908,442
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to options outstanding	$ 0
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)					5,108,000	9,608,000
Number of common stock reserved for future grants (in shares)	646,633
2020 Plan \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)	3,108,438
2020 Plan \| Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)	1,448,053
Prior Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)						107,903
Purchase of common stock (in shares)	108,389
Prior Plans \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards outstanding (in shares)	0
ESPP common stock equivalents
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)							1,000,000
Number of common stock reserved for future grants (in shares)	6,020
Issuance of common stock under employee stock purchase plan (in shares)	993,980
Discount rate from market price, offering date	15.00%
Recognized compensation expense	$ 0	$ 0
Director Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)								1,500,000
Number of common stock reserved for future grants (in shares)	0
Director Plan \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase of common stock (in shares)	56,443

MITEK SYSTEMS INC 10-Q