Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 08, 2018
Document Information [Line Items]
Entity Registrant Name	CUMULUS MEDIA INC
Trading Symbol	CMLS
Entity Central Index Key	0001058623
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Class A common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		29,225,765
Class C common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		80,609