Document and Entity Information
| Document and Entity Information | Jul. 31, 2020 |
| Document And Entity Information [Line Items] | |
| Entity Registrant Name | CUMULUS MEDIA INC |
| Entity Central Index Key | 0001058623 |
| Document Type | 8-K |
| Document Period End Date | Jul. 31, 2020 |
| Amendment Flag | false |
| Entity Emerging Growth Company | false |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38108 |
| Entity Tax Identification Number | 82-5134717 |
| Entity Address, Address Line One | 3280 Peachtree Road, NW |
| Entity Address, Address Line Two | 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Trading Symbol | CMLS |
| Title of 12(b) Security | Class A common stock, par value $0.0000001 per share |
| Security Exchange Name | NASDAQ |
| Rights [Member] | |
| Document And Entity Information [Line Items] | |
| Title of 12(b) Security | Class A Common Stock Purchase Rights |
| Security Exchange Name | NASDAQ |
| No Trading Symbol Flag | true |