Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 28, 2022	Jun. 30, 2021
Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Document Transition Report	false
Entity File Number	001-14761
Entity Registrant Name	GAMCO INVESTORS, INC. ET AL
Entity Central Index Key	0001060349
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-4007862
Entity Address, Address Line One	191 Mason Street
Entity Address, City or Town	Greenwich
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06830
City Area Code	203
Local Phone Number	629-2726
Title of 12(b) Security	Class A Common Stock, $0.001 par value
Trading Symbol	GBL
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 137,117,912
ICFR Auditor Attestation Flag	true
Auditor Name	Deloitte & Touche, LLP
Auditor Location	Stamford, Connecticut
Auditor Firm ID	34
Class A [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		7,590,811
Class B [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		19,024,117