INCOME TAXES - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Goodwill and other intangibles	$ 8.3	$ 8.4
Inventory	1.3	2.8
Accrued insurance	5.2	4.6
Stock compensation	3.5	2.5
Interest limitation carryover	10.4	6.6
Start-up acquisition costs	2.8	2.7
Other accrued expenses	3.4	3.4
Operating lease liabilities	18.1
Net operating loss (NOL) carryforwards	11.3	8.4
Property, plant and equipment, net - Polaris	3.3	2.9
Other	1.9	3.7
Total gross deferred tax assets	69.5	46.0
Valuation allowance	(15.1)	(9.2)
Net deferred tax assets	54.4	36.8
Deferred income tax liabilities:
Property, plant and equipment, net - non-Polaris	(56.4)	(46.1)
Partnership outside basis	(28.2)	(26.7)
Depletion	0.0	(1.6)
Operating lease assets	(17.9)
Other	(2.2)	(0.4)
Total gross deferred tax liabilities	(104.7)	(74.8)
Net deferred tax liability	(50.3)	(38.0)
State
Deferred tax assets:
Net operating loss (NOL) carryforwards	6.4
Income Tax Examination [Line Items]
Deferred tax assets, gross, noncurrent	4.5	5.1
Domestic and Foreign
Income Tax Examination [Line Items]
Non-current deferred tax liability	$ 54.8	$ 43.1