Revenue - Trade Sale Revenue (Detail) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Trade sales receivable	$ 1,563,809		$ 1,563,809		$ 1,550,172
Trade sales payable	1,315,712		1,315,712		$ 1,276,170
Trade sales revenue	$ 2,790,888	$ 2,144,090	$ 6,409,976	$ 6,916,643

Total revenue recognized from advertising barter transactions for each income statement presented.

No definition available.

Name:	us-gaap_AdvertisingBarterTransactionsAdvertisingBarterRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration