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Commitments and Contingencies (Detail) $ in Millions		1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
Commitments and Contingencies (Detail) $ in Millions	Jan. 02, 2014 USD ($) station	Aug. 31, 2015 lawsuit	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2014 USD ($)
ABS Entertainment, Inc, et al v Cumulus Media Inc and ABS Entertainment, Inc v Cumulus Media Inc \| Pending Litigation
Supply Commitment [Line Items]
Number of punitive class action lawsuits \| lawsuit		2
Exit Plan \| Contract Termination \| Corporate Expenses
Supply Commitment [Line Items]
Restructuring costs					$ 5.2
Exit Plan \| Contract Termination \| Accounts Payable and Accrued Expenses
Supply Commitment [Line Items]
Current restructuring liabilities			$ 0.5	$ 0.5
Exit Plan \| Contract Termination \| Non-current liabilities
Supply Commitment [Line Items]
Noncurrent restructuring liabilities			3.5	3.5
Merlin Media LLC
Supply Commitment [Line Items]
Monthly management fees, second year	$ 0.4
Monthly management fees, third year	0.5
Monthly management fees, fourth year	$ 0.6
Merlin Media LLC \| Put Option
Supply Commitment [Line Items]
Number of radio stations \| station	2
Amount under option agreement to settle management fees	$ 71.0
Period after commencement date to settle management fees	4 years
Period to exercise option	10 days
Merlin Media LLC \| Call Option \| Maximum
Supply Commitment [Line Items]
Amount under option agreement to settle management fees	$ 70.0
Merlin Media LLC \| Call Option \| Minimum
Supply Commitment [Line Items]
Amount under option agreement to settle management fees	$ 50.0
CBS
Supply Commitment [Line Items]
Settlement amount paid			$ 13.3
Nielson Audio
Supply Commitment [Line Items]
Remaining aggregate obligation under the agreements with Nielsen Audio				$ 67.0