SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognitions (Narrative) (Details)	12 Months Ended
Dec. 31, 2017
Maximum
Revenue Recognition, Milestone Method [Line Items]
Outdoor advertising contracts, term	1 year

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.

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