Supplemental Condensed Consolidated Financial Information (Condensed Consolidated Statements of Operations) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Income Statements, Captions [Line Items]
Net revenue	$ 263,679	$ 264,030
Operating expenses:
Content costs	99,815	101,780
Selling, general and administrative expenses	115,134	114,390
Depreciation and amortization	11,981	16,282
Local marketing agreement fees	1,107	2,707
Corporate expenses (including stock-based compensation expense)	10,487	10,955
Loss (gain) on sale or disposal of assets or stations	11	(2,606)
Total operating expenses	238,535	243,508
Operating income	25,144	20,522
Non-operating expense:
Reorganization items, net	(30,167)	0
Interest (expense) income, net	(99)	(34,026)
Other income, net	3	83
Total non-operating expense, net	(30,263)	(33,943)
Loss before income taxes	(5,119)	(13,421)
Income tax benefit (expense)	118	6,026
(Loss) earnings from consolidated subsidiaries	0	0
Net loss	(5,001)	(7,395)
Eliminations
Condensed Income Statements, Captions [Line Items]
Net revenue	0	0
Operating expenses:
Content costs	0	0
Selling, general and administrative expenses	0	0
Depreciation and amortization	0	0
Local marketing agreement fees	0	0
Corporate expenses (including stock-based compensation expense)	0	0
Loss (gain) on sale or disposal of assets or stations	0	0
Total operating expenses	0	0
Operating income	0	0
Non-operating expense:
Reorganization items, net	0
Interest (expense) income, net	0	0
Other income, net	0	0
Total non-operating expense, net	0	0
Loss before income taxes	0	0
Income tax benefit (expense)	0	0
(Loss) earnings from consolidated subsidiaries	(20,302)	(11,132)
Net loss	(20,302)	(11,132)
Cumulus Media Inc. (Parent Guarantor)
Condensed Income Statements, Captions [Line Items]
Net revenue	0	0
Operating expenses:
Content costs	0	0
Selling, general and administrative expenses	0	0
Depreciation and amortization	0	0
Local marketing agreement fees	0	0
Corporate expenses (including stock-based compensation expense)	0	0
Loss (gain) on sale or disposal of assets or stations	0	0
Total operating expenses	0	0
Operating income	0	0
Non-operating expense:
Reorganization items, net	0
Interest (expense) income, net	(2,184)	(2,184)
Other income, net	0	0
Total non-operating expense, net	(2,184)	(2,184)
Loss before income taxes	(2,184)	(2,184)
Income tax benefit (expense)	629	998
(Loss) earnings from consolidated subsidiaries	(3,446)	(6,209)
Net loss	(5,001)	(7,395)
Cumulus Media Holdings Inc. (Subsidiary Issuer)
Condensed Income Statements, Captions [Line Items]
Net revenue	0	0
Operating expenses:
Content costs	0	0
Selling, general and administrative expenses	0	0
Depreciation and amortization	249	303
Local marketing agreement fees	0	0
Corporate expenses (including stock-based compensation expense)	10,487	10,955
Loss (gain) on sale or disposal of assets or stations	0	0
Total operating expenses	10,736	11,258
Operating income	(10,736)	(11,258)
Non-operating expense:
Reorganization items, net	(30,167)
Interest (expense) income, net	2,056	(32,196)
Other income, net	0	0
Total non-operating expense, net	(28,111)	(32,196)
Loss before income taxes	(38,847)	(43,454)
Income tax benefit (expense)	11,188	19,753
(Loss) earnings from consolidated subsidiaries	24,213	17,492
Net loss	(3,446)	(6,209)
Subsidiary Guarantors
Condensed Income Statements, Captions [Line Items]
Net revenue	263,679	264,030
Operating expenses:
Content costs	99,815	101,780
Selling, general and administrative expenses	114,481	113,795
Depreciation and amortization	11,732	15,979
Local marketing agreement fees	1,107	2,707
Corporate expenses (including stock-based compensation expense)	0	0
Loss (gain) on sale or disposal of assets or stations	11	(2,606)
Total operating expenses	227,146	231,655
Operating income	36,533	32,375
Non-operating expense:
Reorganization items, net	0
Interest (expense) income, net	29	37
Other income, net	3	83
Total non-operating expense, net	32	120
Loss before income taxes	36,565	32,495
Income tax benefit (expense)	(11,887)	(14,852)
(Loss) earnings from consolidated subsidiaries	(465)	(151)
Net loss	24,213	17,492
Subsidiary Non-guarantors
Condensed Income Statements, Captions [Line Items]
Net revenue	0	0
Operating expenses:
Content costs	0	0
Selling, general and administrative expenses	653	595
Depreciation and amortization	0	0
Local marketing agreement fees	0	0
Corporate expenses (including stock-based compensation expense)	0	0
Loss (gain) on sale or disposal of assets or stations	0	0
Total operating expenses	653	595
Operating income	(653)	(595)
Non-operating expense:
Reorganization items, net	0
Interest (expense) income, net	0	317
Other income, net	0	0
Total non-operating expense, net	0	317
Loss before income taxes	(653)	(278)
Income tax benefit (expense)	188	127
(Loss) earnings from consolidated subsidiaries	0	0
Net loss	$ (465)	$ (151)