INCOME TAXES - Federal Tax Rate Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of federal income taxes at the applicable statutory rate to the recorded provision from continuing operations
Federal statutory rate (as a percent)		21.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent [Abstract]
Federal tax reform (as a percent)		(19.90%)	(2.20%)	(0.40%)
State income taxes, net of federal tax benefit (as a percent)		(9.00%)	5.00%	0.20%
Non-deductible items (as a percent)		(4.90%)	1.50%	1.00%
Effect of consolidated VIEs (as a percent)		1.60%	1.00%	1.20%
Federal tax reform (as a percent)		(1.40%)	(54.30%)	0.00%
Domestic production activities deduction (as a percent)		0.00%	(1.70%)	(3.40%)
Other (as a percent)		0.90%	0.60%	(0.30%)
Effective income tax rate (as a percent)		(11.70%)	(15.10%)	33.30%
Benefit from investment tax credits		$ 58.2	$ 8.3
Benefit from gain on sale of certain broadcast spectrum		17.7
Federal tax reform	$ 272.1	$ 4.3	$ 272.1