Document And Entity Information - shares	6 Months Ended
	Sep. 30, 2025	Nov. 13, 2025
Document Information [Line Items]
Entity Central Index Key	0001000045
Entity Registrant Name	OLD MARKET CAPITAL Corp
Amendment Flag	false
Current Fiscal Year End Date	--03-31
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2026
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2025
Document Transition Report	false
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, 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
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		6,790,097