Supplemental Condensed Consolidated Financial Information (Condensed Consolidated Statements of Cash Flows) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net (loss) income	$ (5,001)	$ (7,395)
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	11,981	16,282
Amortization of debt issuance costs/discounts		2,510
Provision for doubtful accounts	1,105	709
Loss (gain) on sale or disposal of assets or stations	11	(2,606)
Deferred income taxes	(118)	(6,030)
Stock-based compensation expense	166	538
Loss (earnings) from consolidated subsidiaries	0	0
Changes in assets and liabilities	40,228	15,417
Net cash provided by operating activities	48,372	19,425
Cash flows from investing activities:
Proceeds from sale of assets or stations	0	6,090
Restricted cash		0
Capital expenditures	(9,005)	(5,736)
Net cash (used in) provided by investing activities	(9,005)	354
Cash flows from financing activities:
Intercompany transactions, net	0	0
Repayments of borrowings under term loans and revolving credit facilities	(22,131)	0
Deferred financing costs	0	(94)
Net cash used in financing activities	(22,131)	(94)
Increase in cash and cash equivalents and restricted cash	17,236	19,685
Cash and cash equivalents and restricted cash at beginning of period	111,890	139,284
Cash and cash equivalents and restricted cash at end of period	129,126	158,969
Eliminations
Cash flows from operating activities:
Net (loss) income	(20,302)	(11,132)
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	0	0
Amortization of debt issuance costs/discounts		0
Provision for doubtful accounts	0	0
Loss (gain) on sale or disposal of assets or stations	0	0
Deferred income taxes	0	0
Stock-based compensation expense	0	0
Loss (earnings) from consolidated subsidiaries	20,302	11,132
Changes in assets and liabilities	0	0
Net cash provided by operating activities	0	0
Cash flows from investing activities:
Proceeds from sale of assets or stations		0
Restricted cash		0
Capital expenditures	0	0
Net cash (used in) provided by investing activities	0	0
Cash flows from financing activities:
Intercompany transactions, net	0	0
Repayments of borrowings under term loans and revolving credit facilities	0
Deferred financing costs		0
Net cash used in financing activities	0	0
Increase in cash and cash equivalents and restricted cash	0	0
Cash and cash equivalents and restricted cash at beginning of period	0	0
Cash and cash equivalents and restricted cash at end of period	0	0
Cumulus Media Inc. (Parent Guarantor)
Cash flows from operating activities:
Net (loss) income	(5,001)	(7,395)
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	0	0
Amortization of debt issuance costs/discounts		0
Provision for doubtful accounts	0	0
Loss (gain) on sale or disposal of assets or stations	0	0
Deferred income taxes	(629)	(998)
Stock-based compensation expense	0	0
Loss (earnings) from consolidated subsidiaries	3,446	6,209
Changes in assets and liabilities	(2,196)	0
Net cash provided by operating activities	(4,380)	(2,184)
Cash flows from investing activities:
Proceeds from sale of assets or stations		0
Restricted cash		0
Capital expenditures	0	0
Net cash (used in) provided by investing activities	0	0
Cash flows from financing activities:
Intercompany transactions, net	4,380	2,184
Repayments of borrowings under term loans and revolving credit facilities	0
Deferred financing costs		0
Net cash used in financing activities	4,380	2,184
Increase in cash and cash equivalents and restricted cash	0	0
Cash and cash equivalents and restricted cash at beginning of period	0	0
Cash and cash equivalents and restricted cash at end of period	0	0
Cumulus Media Holdings Inc. (Subsidiary Issuer)
Cash flows from operating activities:
Net (loss) income	(3,446)	(6,209)
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	249	303
Amortization of debt issuance costs/discounts		2,463
Provision for doubtful accounts	0	0
Loss (gain) on sale or disposal of assets or stations	0	0
Deferred income taxes	(11,188)	(19,753)
Stock-based compensation expense	166	538
Loss (earnings) from consolidated subsidiaries	(24,213)	(17,492)
Changes in assets and liabilities	88,741	108,895
Net cash provided by operating activities	50,309	68,745
Cash flows from investing activities:
Proceeds from sale of assets or stations		0
Restricted cash		0
Capital expenditures	(6,395)	(2,441)
Net cash (used in) provided by investing activities	(6,395)	(2,441)
Cash flows from financing activities:
Intercompany transactions, net	(4,547)	(46,525)
Repayments of borrowings under term loans and revolving credit facilities	(22,131)
Deferred financing costs		(94)
Net cash used in financing activities	(26,678)	(46,619)
Increase in cash and cash equivalents and restricted cash	17,236	19,685
Cash and cash equivalents and restricted cash at beginning of period	111,890	139,284
Cash and cash equivalents and restricted cash at end of period	129,126	158,969
Subsidiary Guarantors
Cash flows from operating activities:
Net (loss) income	24,213	17,492
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	11,732	15,979
Amortization of debt issuance costs/discounts		0
Provision for doubtful accounts	1,105	709
Loss (gain) on sale or disposal of assets or stations	11	(2,606)
Deferred income taxes	11,887	14,848
Stock-based compensation expense	0	0
Loss (earnings) from consolidated subsidiaries	465	151
Changes in assets and liabilities	(46,970)	(93,709)
Net cash provided by operating activities	2,443	(47,136)
Cash flows from investing activities:
Proceeds from sale of assets or stations		6,090
Restricted cash		0
Capital expenditures	(2,610)	(3,295)
Net cash (used in) provided by investing activities	(2,610)	2,795
Cash flows from financing activities:
Intercompany transactions, net	167	44,341
Repayments of borrowings under term loans and revolving credit facilities	0
Deferred financing costs		0
Net cash used in financing activities	167	44,341
Increase in cash and cash equivalents and restricted cash	0	0
Cash and cash equivalents and restricted cash at beginning of period	0	0
Cash and cash equivalents and restricted cash at end of period	0	0
Subsidiary Non-guarantors
Cash flows from operating activities:
Net (loss) income	(465)	(151)
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization	0	0
Amortization of debt issuance costs/discounts		47
Provision for doubtful accounts	0	0
Loss (gain) on sale or disposal of assets or stations	0	0
Deferred income taxes	(188)	(127)
Stock-based compensation expense	0	0
Loss (earnings) from consolidated subsidiaries	0	0
Changes in assets and liabilities	653	231
Net cash provided by operating activities	0	0
Cash flows from investing activities:
Proceeds from sale of assets or stations		0
Restricted cash		0
Capital expenditures	0	0
Net cash (used in) provided by investing activities	0	0
Cash flows from financing activities:
Intercompany transactions, net	0	0
Repayments of borrowings under term loans and revolving credit facilities	0
Deferred financing costs		0
Net cash used in financing activities	0	0
Increase in cash and cash equivalents and restricted cash	0	0
Cash and cash equivalents and restricted cash at beginning of period	0	0
Cash and cash equivalents and restricted cash at end of period	$ 0	$ 0