Commitments and Contingencies	3 Months Ended
Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Rothschild Mobile Imaging Innovations, Inc. On May 16, 2014, Rothschild Mobile Imaging Innovations, Inc. (“RMII”) filed a complaint against the Company in the U.S. District Court for the District of Delaware alleging that certain of the Company’s mobile imaging products infringe four RMII-owned patents related to mobile imaging technology. On June 1, 2014, RMII amended its complaint to add JPMorgan Chase & Co. and JPMorgan Chase Bank, N.A. (together, “Chase”), one of the Company’s customers, as a defendant in the lawsuit (as amended, the “Initial Lawsuit”). On September 8, 2014, RMII filed three additional complaints (the “Subsequent Lawsuits”) against the Company in the U.S. District Court for the District of Delaware. The Subsequent Lawsuits contain allegations substantially similar to the Initial Lawsuit regarding infringement by the Company’s mobile imaging products of the four RMII-owned patents related to mobile imaging technology, but name as co-defendants Citibank, N.A., Citigroup Inc., Wells Fargo & Company, Wells Fargo Bank, N.A., Bank of America Corporation and Bank of America, N.A., respectively (together with Chase, the “Bank Defendants”). RMII subsequently filed amended complaints (together with the Initial Lawsuit and the Subsequent Lawsuits, the “RMII Lawsuits”) adding as defendants both Fiserv and NCR (the “Distributor Defendants”), each of whom distributes the Company’s mobile imaging technology to one or more of the Bank Defendants. Based on the Company’s understanding of the claims, the Company agreed to accept the demands for indemnity and defense tendered by each of the Bank Defendants and Distributor Defendants in connection with the RMII Lawsuits. On November 10, 2014, the Company filed a motion to sever and stay the claims against Chase in the Initial Lawsuit pending resolution of RMII’s claims against the Company, which motion was granted on August 3, 2015. On November 19, 2014, the Company filed joinders to the motion to stay with respect to the Subsequent Lawsuits, which joinders were also granted on August 3, 2015. Additionally, the Patent Trial and Appeal Board (“PTAB”) of the Patent and Trademark Office instituted the Company’s petitions for Inter Partes Review (“IPR”) challenging the patentability of all four asserted patents, and the Court agreed to stay the litigation in its entirety until all of the decisions are rendered in the IPR proceedings. On July 20, 2016, the PTAB entered its final decision in the IPR proceedings. The PTAB ruled that all claims asserted in the litigation in all four RMII patents were directed to unpatentable subject matter and thus not patent eligible. On September 16, 2016, the parties filed a joint status report notifying the Court of the PTAB’s decisions in the IPRs. Through that notice, Mitek requested that the Court enter a judgment of non-infringement, or, in the alternative, dismiss all of RMII’s claims against all defendants with prejudice. On September 16, 2016, RMII filed a motion to dismiss without prejudice. On September 15, 2017, the Court granted the motion, but dismissed the cases with prejudice. On September 29, 2017, Mitek filed a motion for attorneys' fees and expenses. RMII recently filed a response to that motion. Other Legal Matters In addition to the foregoing, the Company is subject to various claims and legal proceedings arising in the ordinary course of its business. The Company accrues for such liabilities when it is both (i) probable that a loss has occurred and (ii) the amount of the loss can be reasonably estimated in accordance with ASC 450. While any legal proceeding has an element of uncertainty, the Company believes that the disposition of such matters, in the aggregate, will not have a material effect on the Company’s financial condition or results of operations. Facility Leases The Company’s principal executive offices, as well as its research and development facility, are located in approximately 28,791 square feet of office space in San Diego, California and the term of the lease for the Company’s offices continues through June 30, 2024. The average annual base rent under this lease is approximately $1.0 million per year. In connection with this lease, the Company received tenant improvement allowances totaling $1.0 million. These lease incentives are being amortized as a reduction of rent expense over the term of the lease. As of December 31, 2017, the unamortized balance of the lease incentives was $0.9 million, of which $0.1 million has been included in other current liabilities and $0.8 million has been included in other non-current liabilities. The offices of IDchecker are located in the Netherlands and the term of this lease continues through May 31, 2018 with annual base rent of approximately €48,000 (or approximately $57,000) per year. In December IDchecker signed a new lease for a new office building. This lease continues through December 31, 2023 with annual base rent of approximately €197,000 (or approximately $236,000) per year. The Company has a sales office in London, UK. The term of this lease continues through May 31, 2018. The annual base rent under this lease is approximately £77,000 (or approximately $104,000) per year. The Company believes its existing properties are in good condition and are sufficient and suitable for the conduct of its business.

COMMITMENTS AND CONTINGENCIES

Rothschild Mobile Imaging Innovations, Inc.

On May 16, 2014, Rothschild Mobile Imaging Innovations, Inc. (“RMII”) filed a complaint against the Company in the U.S. District Court for the District of Delaware alleging that certain of the Company’s mobile imaging products infringe four RMII-owned patents related to mobile imaging technology. On June 1, 2014, RMII amended its complaint to add JPMorgan Chase & Co. and JPMorgan Chase Bank, N.A. (together, “Chase”), one of the Company’s customers, as a defendant in the lawsuit (as amended, the “Initial Lawsuit”). On September 8, 2014, RMII filed three additional complaints (the “Subsequent Lawsuits”) against the Company in the U.S. District Court for the District of Delaware. The Subsequent Lawsuits contain allegations substantially similar to the Initial Lawsuit regarding infringement by the Company’s mobile imaging products of the four RMII-owned patents related to mobile imaging technology, but name as co-defendants Citibank, N.A., Citigroup Inc., Wells Fargo & Company, Wells Fargo Bank, N.A., Bank of America Corporation and Bank of America, N.A., respectively (together with Chase, the “Bank Defendants”). RMII subsequently filed amended complaints (together with the Initial Lawsuit and the Subsequent Lawsuits, the “RMII Lawsuits”) adding as defendants both Fiserv and NCR (the “Distributor Defendants”), each of whom distributes the Company’s mobile imaging technology to one or more of the Bank Defendants. Based on the Company’s understanding of the claims, the Company agreed to accept the demands for indemnity and defense tendered by each of the Bank Defendants and Distributor Defendants in connection with the RMII Lawsuits.

On November 10, 2014, the Company filed a motion to sever and stay the claims against Chase in the Initial Lawsuit pending resolution of RMII’s claims against the Company, which motion was granted on August 3, 2015. On November 19, 2014, the Company filed joinders to the motion to stay with respect to the Subsequent Lawsuits, which joinders were also granted on August 3, 2015. Additionally, the Patent Trial and Appeal Board (“PTAB”) of the Patent and Trademark Office instituted the Company’s petitions for Inter Partes Review (“IPR”) challenging the patentability of all four asserted patents, and the Court agreed to stay the litigation in its entirety until all of the decisions are rendered in the IPR proceedings.

On July 20, 2016, the PTAB entered its final decision in the IPR proceedings. The PTAB ruled that all claims asserted in the litigation in all four RMII patents were directed to unpatentable subject matter and thus not patent eligible. On September 16, 2016, the parties filed a joint status report notifying the Court of the PTAB’s decisions in the IPRs. Through that notice, Mitek requested that the Court enter a judgment of non-infringement, or, in the alternative, dismiss all of RMII’s claims against all defendants with prejudice. On September 16, 2016, RMII filed a motion to dismiss without prejudice. On September 15, 2017, the Court granted the motion, but dismissed the cases with prejudice. On September 29, 2017, Mitek filed a motion for attorneys' fees and expenses. RMII recently filed a response to that motion.

Other Legal Matters

In addition to the foregoing, the Company is subject to various claims and legal proceedings arising in the ordinary course of its business. The Company accrues for such liabilities when it is both (i) probable that a loss has occurred and (ii) the amount of the loss can be reasonably estimated in accordance with ASC 450. While any legal proceeding has an element of uncertainty, the Company believes that the disposition of such matters, in the aggregate, will not have a material effect on the Company’s financial condition or results of operations.

Facility Leases

The Company’s principal executive offices, as well as its research and development facility, are located in approximately 28,791 square feet of office space in San Diego, California and the term of the lease for the Company’s offices continues through June 30, 2024. The average annual base rent under this lease is approximately $1.0 million per year. In connection with this lease, the Company received tenant improvement allowances totaling $1.0 million. These lease incentives are being amortized as a reduction of rent expense over the term of the lease. As of December 31, 2017, the unamortized balance of the lease incentives was $0.9 million, of which $0.1 million has been included in other current liabilities and $0.8 million has been included in other non-current liabilities. The offices of IDchecker are located in the Netherlands and the term of this lease continues through May 31, 2018 with annual base rent of approximately €48,000 (or approximately $57,000) per year. In December IDchecker signed a new lease for a new office building. This lease continues through December 31, 2023 with annual base rent of approximately €197,000 (or approximately $236,000) per year. The Company has a sales office in London, UK. The term of this lease continues through May 31, 2018. The annual base rent under this lease is approximately £77,000 (or approximately $104,000) per year. The Company believes its existing properties are in good condition and are sufficient and suitable for the conduct of its business.