INCOME TAXES - Reconciliation Between Income Tax Expense and Computed Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax at Federal statutory rate	$ 13.9	$ 13.2	$ 15.9
State and local income taxes, net of federal tax benefit	2.4	2.6	5.0
Impact of state rate changes	0.1	(0.1)	0.3
Changes in valuation allowances	0.0	0.0	(21.7)
Reversal of valuation allowances	(0.3)	(0.2)	(29.4)
2017 TCJA, net deferred tax remeasurement and repatriation tax impacts	0.0	0.0	10.4
Stock based compensation	(0.5)	(1.5)	0.0
Non-deductible items	0.8	0.1	0.1
Other items, net	(0.3)	(0.7)	(0.6)
Income tax	$ 16.1	$ 13.4	$ (20.0)
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income tax at Federal statutory rate	21.00%	21.00%	35.00%
State and local income taxes, net of federal tax benefit	3.70%	4.10%	11.00%
Impact of state rate changes	0.10%	(0.20%)	0.70%
Changes in valuation allowances	0.00%	0.00%	(47.70%)
Reversal of valuation allowances	(0.40%)	(0.30%)	(64.60%)
2017 TCJA, net deferred tax remeasurement and repatriation tax impacts	0.00%	0.00%	22.90%
Stock based compensation	(0.80%)	(2.40%)	0.00%
Non-deductible items	1.20%	0.20%	0.20%
Other items, net	(0.40%)	(1.10%)	(1.50%)
Income tax	24.40%	21.30%	(44.00%)