INCOME TAXES - Federal Tax Rate Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of federal income taxes at the applicable statutory rate to the recorded provision from continuing operations
Federal statutory rate (as a percent)		35.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent [Abstract]
Federal tax reform (as a percent)		(54.30%)	0.00%	0.00%
State income taxes, net of federal tax benefit (as a percent)		5.00%	0.20%	0.60%
Non-deductible items (as a percent)		1.50%	1.00%	1.20%
Domestic production activities deduction (as a percent)		(1.70%)	(3.40%)	(3.90%)
Changes in unrecognized tax benefits (as a percent)		0.50%	0.30%	(1.90%)
Basis in stock subsidiaries (as a percent)		0.00%	0.00%	(5.50%)
Federal tax credits (as a percent)		(2.20%)	(0.40%)	(1.10%)
Other (as a percent)		1.10%	0.60%	0.80%
Effective income tax rate (as a percent)		(15.10%)	33.30%	25.20%
Federal tax reform	$ 272.1	$ 272.1
Reductions related to expiration of the applicable statute of limitations		0.1	$ 1.0	$ 5.7
Tax benefit realized, sale of stock of subsidiary				12.6
Benefit from investment tax credits		8.3
Benefit from research tax credits		$ 2.5	$ 1.6	$ 1.1