DEBT - SUMMARY (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Aug. 31, 2004	Sep. 30, 2003
Debt
Capital leases	$ 0.1	$ 0.8
Total Debt	856.4	857.1
Less current portion	(42.1)	(30.8)
Total Long-term Debt	814.3	826.3
5.79%, payable through 2020
Debt
Total Debt	$ 10.5	17.5
Interest rate (as a percent)	5.79%
3.66%, payable through 2023
Debt
Total Debt	$ 41.0	50.1
Interest rate (as a percent)	3.66%
4.16%, payable through 2027
Debt
Total Debt	$ 44.5	49.8
Interest rate (as a percent)	4.16%
3.37 %, payable through 2027
Debt
Total Debt	$ 75.0	75.0
Interest rate (as a percent)	3.37%
3.14%, payable through 2031
Debt
Total Debt	$ 200.0	200.0
Interest rate (as a percent)	3.14%
4.31%, payable through 2032
Debt
Total Debt	$ 32.7	35.1
Interest rate (as a percent)	4.31%
4.35%, payable through 2044
Debt
Total Debt	$ 100.0	100.0
Interest rate (as a percent)	4.35%
3.92%, payable through 2045
Debt
Total Debt	$ 71.4	73.2
Interest rate (as a percent)	3.92%
5.34%, payable through 2028
Debt
Total Debt	$ 22.0	24.2
Interest rate (as a percent)	5.34%			5.34%
5.27%, payable through 2029
Debt
Total Debt	$ 24.2	26.4
Interest rate (as a percent)	5.27%		5.27%
Revolving Credit Facility
Debt
Total Debt	$ 235.0	$ 205.0
Funds available under the revolving credit facility	$ 304.0
Interest rate during period (as a percent)	3.92%