SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION - Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 40.6	$ 20.0
Trade accounts receivable, net	233.1	226.6
Inventories	59.0	51.2
Other receivables, net	8.4	18.4
Prepaid expenses and other	7.9	7.9
Intercompany receivables	0.0	0.0
Total current assets	349.0	324.1
Property, plant and equipment, net	673.5
Property, plant and equipment, net		680.2	$ 636.3
Operating lease assets	69.8
Goodwill	239.5	239.3	204.7
Intangible assets, net	92.4	116.6
Investment in subsidiaries	0.0	0.0
Long-term intercompany receivables	0.0	0.0
Other assets	9.1	11.1
Total assets	1,433.3	1,371.3
Current liabilities:
Accounts payable	136.4	125.8
Accrued liabilities	63.5	96.3
Current maturities of long-term debt	32.5	30.8
Current operating lease liabilities	12.9
Intercompany payables	0.0	0.0
Total current liabilities	245.3	252.9
Long-term debt, net of current maturities	654.8	683.3
Long-term operating lease liabilities	59.7
Other long-term obligations and deferred credits	49.1	54.8
Deferred income taxes	54.8	43.1
Long-term intercompany payables	0.0	0.0
Total liabilities	1,063.7	1,034.1
Total shareholders' equity	343.4	312.4
Non-controlling interest (Note 12)	26.2	24.8
Total equity	369.6	337.2	$ 302.1	$ 188.8
Total liabilities and equity	1,433.3	1,371.3
Eliminations and Reclassifications
Current assets:
Cash and cash equivalents	0.0	0.0
Trade accounts receivable, net	0.0	0.0
Inventories	0.0	0.0
Other receivables, net	(13.3)	0.0
Prepaid expenses and other	0.0	0.0
Intercompany receivables	(9.2)	(10.0)
Total current assets	(22.5)	(10.0)
Property, plant and equipment, net	0.0
Property, plant and equipment, net		0.0
Operating lease assets	0.0
Goodwill	0.0	0.0
Intangible assets, net	0.0	0.0
Investment in subsidiaries	(642.6)	(604.1)
Long-term intercompany receivables	(287.1)	(310.0)
Other assets	0.0	0.0
Total assets	(952.2)	(924.1)
Current liabilities:
Accounts payable	0.0	0.0
Accrued liabilities	(13.3)	0.0
Current maturities of long-term debt	0.0	0.0
Current operating lease liabilities	0.0
Intercompany payables	(9.2)	(10.0)
Total current liabilities	(22.5)	(10.0)
Long-term debt, net of current maturities	0.0	0.0
Long-term operating lease liabilities	0.0
Other long-term obligations and deferred credits	0.0	0.0
Deferred income taxes	0.0	0.0
Long-term intercompany payables	(287.1)	(310.0)
Total liabilities	(309.6)	(320.0)
Total shareholders' equity	(642.6)	(604.1)
Non-controlling interest (Note 12)	0.0	0.0
Total equity	(642.6)	(604.1)
Total liabilities and equity	(952.2)	(924.1)
Parent | Reportable Legal Entities
Current assets:
Cash and cash equivalents	0.0	0.0
Trade accounts receivable, net	0.0	0.0
Inventories	0.0	0.0
Other receivables, net	15.1	11.1
Prepaid expenses and other	0.0	0.0
Intercompany receivables	8.9	9.7
Total current assets	24.0	20.8
Property, plant and equipment, net	0.0
Property, plant and equipment, net		0.0
Operating lease assets	0.0
Goodwill	0.0	0.0
Intangible assets, net	0.0	0.0
Investment in subsidiaries	642.6	604.1
Long-term intercompany receivables	281.8	308.9
Other assets	0.0	0.0
Total assets	948.4	933.8
Current liabilities:
Accounts payable	0.0	0.0
Accrued liabilities	4.3	4.7
Current maturities of long-term debt	0.3	0.3
Current operating lease liabilities	0.0
Intercompany payables	0.0	0.0
Total current liabilities	4.6	5.0
Long-term debt, net of current maturities	600.4	615.5
Long-term operating lease liabilities	0.0
Other long-term obligations and deferred credits	0.0	0.9
Deferred income taxes	0.0	0.0
Long-term intercompany payables	0.0	0.0
Total liabilities	605.0	621.4
Total shareholders' equity	343.4	312.4
Non-controlling interest (Note 12)	0.0	0.0
Total equity	343.4	312.4
Total liabilities and equity	948.4	933.8
Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash and cash equivalents	29.0	10.8
Trade accounts receivable, net	216.6	219.7
Inventories	45.9	42.4
Other receivables, net	6.3	7.0
Prepaid expenses and other	7.3	7.1
Intercompany receivables	0.0	0.0
Total current assets	305.1	287.0
Property, plant and equipment, net	470.3
Property, plant and equipment, net		468.3
Operating lease assets	55.8
Goodwill	155.7	155.5
Intangible assets, net	88.2	111.8
Investment in subsidiaries	0.0	0.0
Long-term intercompany receivables	0.0	0.0
Other assets	8.0	10.8
Total assets	1,083.1	1,033.4
Current liabilities:
Accounts payable	134.4	122.4
Accrued liabilities	64.0	83.2
Current maturities of long-term debt	31.7	29.9
Current operating lease liabilities	11.2
Intercompany payables	0.0	0.0
Total current liabilities	241.3	235.5
Long-term debt, net of current maturities	52.9	67.6
Long-term operating lease liabilities	47.1
Other long-term obligations and deferred credits	44.2	51.0
Deferred income taxes	28.9	22.4
Long-term intercompany payables	170.4	188.7
Total liabilities	584.8	565.2
Total shareholders' equity	498.3	468.2
Non-controlling interest (Note 12)	0.0	0.0
Total equity	498.3	468.2
Total liabilities and equity	1,083.1	1,033.4
Non-Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash and cash equivalents	11.6	9.2
Trade accounts receivable, net	16.5	6.9
Inventories	13.1	8.8
Other receivables, net	0.3	0.3
Prepaid expenses and other	0.6	0.8
Intercompany receivables	0.3	0.3
Total current assets	42.4	26.3
Property, plant and equipment, net	203.2
Property, plant and equipment, net		211.9
Operating lease assets	14.0
Goodwill	83.8	83.8
Intangible assets, net	4.2	4.8
Investment in subsidiaries	0.0	0.0
Long-term intercompany receivables	5.3	1.1
Other assets	1.1	0.3
Total assets	354.0	328.2
Current liabilities:
Accounts payable	2.0	3.4
Accrued liabilities	8.5	8.4
Current maturities of long-term debt	0.5	0.6
Current operating lease liabilities	1.7
Intercompany payables	9.2	10.0
Total current liabilities	21.9	22.4
Long-term debt, net of current maturities	1.5	0.2
Long-term operating lease liabilities	12.6
Other long-term obligations and deferred credits	4.9	2.9
Deferred income taxes	25.9	20.7
Long-term intercompany payables	116.7	121.3
Total liabilities	183.5	167.5
Total shareholders' equity	144.3	135.9
Non-controlling interest (Note 12)	26.2	24.8
Total equity	170.5	160.7
Total liabilities and equity	$ 354.0	$ 328.2