Cover - shares	9 Months Ended
	Sep. 30, 2020	Oct. 29, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-38108
Entity Registrant Name	Cumulus Media Inc
Entity Central Index Key	0001058623
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-5134717
Entity Address, Address Line One	3280 Peachtree Road,
Entity Address, Address Line Two	NW Suite 2200
Entity Address, City or Town	Atlanta,
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30305
City Area Code	404
Local Phone Number	949-0700
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 Bankruptcy Proceedings, Reporting Current	true
Class A Common Stock
Entity Information [Line Items]
Title of 12(b) Security	Class A common stock, par value $0.0000001 per share
Trading Symbol	CMLS
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		17,930,745
Class B Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		2,416,253
Class A common stock purchase rights
Entity Information [Line Items]
No Trading Symbol Flag	true
Title of 12(b) Security	Class A common stock purchase rights
Security Exchange Name	NASDAQ