Cover Page - shares	9 Months Ended
	Sep. 30, 2022	Oct. 26, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2022
Document Transition Report	false
Entity File Number	000-24498
Entity Registrant Name	DIAMOND HILL INVESTMENT GROUP, INC.
Entity Incorporation, State or Country Code	OH
Entity Tax Identification Number	65-0190407
Entity Address, Address Line One	325 John H. McConnell Blvd., Suite 200
Entity Address, City or Town	Columbus
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	43215
City Area Code	614
Local Phone Number	255-3333
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock, no par value
Trading Symbol	DHIL
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		3,015,855
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Entity Central Index Key	0000909108
Current Fiscal Year End Date	--12-31