SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Principles of Consolidation (Narrative) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) trust	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Direct operating expenses	$ 631,094	$ 595,576	$ 617,246	$ 568,371	$ 651,108	$ 627,150	$ 615,163	$ 577,692	$ 2,412,287	$ 2,471,113	$ 2,540,035
Selling, general and administrative expenses recorded to correct for accounting errors	$ 444,050	$ 421,700	$ 434,581	$ 425,568	433,483	$ 429,426	$ 424,562	$ 416,881	$ 1,725,899	$ 1,704,352	$ 1,680,938
Number of trusts of which the Company is the beneficiary | trust									2
Expenses recorded to correct for accounting errors | Restatement Adjustment | International Outdoor Advertising
Segment Reporting Information [Line Items]
Direct operating expenses					8,200
Selling, general and administrative expenses recorded to correct for accounting errors					$ 3,200