Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2012	Jun. 29, 2012	Mar. 11, 2013 Class A Common Stock	Mar. 11, 2013 Class B Common Stock	Mar. 11, 2013 Class C Common Stock
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY
Trading Symbol	CMLS
Entity Registrant Name	CUMULUS MEDIA INC
Entity Central Index Key	0001058623
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding			159,488,009	15,424,944	644,871
Entity Public Float		$ 223,000,000