Document and Entity Information (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Jun. 28, 2013	Mar. 03, 2014 Class A Common Stock	Mar. 03, 2014 Class B Common Stock	Mar. 03, 2014 Class C Common Stock
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2013
Document Fiscal Year Focus	2013
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			213,689,484	3,315,238	644,871
Entity Public Float		$ 320.9