Document and Entity Information - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Mar. 31, 2025	Jun. 23, 2025	Sep. 30, 2024
Cover [Abstract]
Entity Registrant Name	OLD MARKET CAPITAL CORPORATION
Entity Central Index Key	0001000045
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--03-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Document Type	10-K/A
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2025
Amendment Flag	true
Amendment Description	The purpose of this Amendment No. 2 on Form 10-K/A (this “Amendment”) is to amend and restate Part IV, Item 15, of the previously filed Annual Report on Form 10-K of Old Market Capital Corporation (the “Company”) for the fiscal year ended March 31, 2025, filed with the Securities and Exchange Commission (the “SEC”) on June 30, 2025 (the “Original Form 10-K”) and as amended by that certain Amendment No. 1 on Form 10-K/A also filed with the SEC on June 30, 2025 (“Amendment No. 1”), to clarify certain disclosures in Part IV, Item 15 and include certain exhibits in Part IV, Item 15 that were inadvertently omitted from the Original Form 10-K. Accordingly, Part IV of the Original Form 10-K is hereby amended and restated as set forth herein. As required by Rule 12b-15 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), new certifications by the Company’s principal executive officer and principal financial officer are filed herewith as exhibits to this Amendment pursuant to Rule 13a-14(a) or 15d-14(a) of the Exchange Act. As no financial statements have been included in this Amendment and this Amendment does not contain or amend any disclosure with respect to Items 307 and 308 of Regulation S-K, paragraphs 3, 4, and 5 of the certifications have been omitted. Additionally, because this Amendment does not include financial statements, the Company is not including certifications pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. Except as described above, no other portion of the Original Form 10-K or Amendment No. 1 is being amended and this Amendment does not reflect any events occurring after the filing of the Original Form 10-K. Among other things, forward-looking statements made in the Original Form 10-K have not been revised to reflect events that occurred or facts that became known to us after the filing of the Original Form 10-K, and such forward-looking statements should be read in their historical context. Accordingly, this Amendment should be read together with the Original Form 10-K, Amendment No. 1 and the Company’s other filings made with the SEC.
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	FY
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Document Financial Statement Error Correction [Flag]	false
Entity Interactive Data Current	Yes
Entity File Number	0-26680
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	59-2506879
Entity Address, Address Line One	1601 Dodge Street
Entity Address, Address Line Two	Suite 3350
Entity Address, City or Town	Omaha
Entity Address, State or Province	NE
Entity Address, Postal Zip Code	68102
City Area Code	531
Local Phone Number	867-3631
Title of 12(b) Security	Common Stock
Trading Symbol	OMCC
Security Exchange Name	NASDAQ
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement for the 2025 Annual General Meeting of Shareholders are incorporated by reference into Part III, Items 10 through 14, of the registrant's Annual Report on Form 10-K.
Entity Public Float			$ 42.3
Entity Common Stock, Shares Outstanding		6.7

OLD MARKET CAPITAL Corp 10-K/A