SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 2,474,549	$ 2,438,662	$ 2,451,081	$ 2,396,567	$ 2,454,940	$ 2,417,801	$ 2,364,153	$ 2,329,714	$ 9,760,859	$ 9,566,608	$ 9,306,950
Video
Disaggregation of Revenue [Line Items]
Total revenue		993,158	1,018,426	1,017,330	1,033,649	1,054,667	1,034,404	1,033,708	3,997,873	4,156,428	4,274,122
Broadband
Disaggregation of Revenue [Line Items]
Total revenue		814,328	806,250	775,573	743,725	729,907	712,202	701,621	3,222,605	2,887,455	2,608,595
Telephony
Disaggregation of Revenue [Line Items]
Total revenue		148,231	150,232	154,464	162,007	161,351	163,499	166,038	598,694	652,895	700,765
Business services and wholesale
Disaggregation of Revenue [Line Items]
Total revenue		357,628	357,806	350,689	348,087	344,193	337,388	333,090	1,428,532	1,362,758	1,298,213
Advertising and News [Member]
Disaggregation of Revenue [Line Items]
Total revenue		118,067	114,450	94,738	$ 163,272	$ 123,913	$ 111,342	$ 88,737	475,904	487,264	396,187
Mobile [Member]
Disaggregation of Revenue [Line Items]
Total revenue		$ 3,174	$ 0	$ 0					21,264	0	0
Other
Disaggregation of Revenue [Line Items]
Total revenue									$ 15,987	$ 19,808	$ 29,068