Broadcast Licenses - Additional Information (Detail)	3 Months Ended
Mar. 31, 2019
Broadcast Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
License renewable term	8 years

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration