SEGMENT AND GEOGRAPHIC INFORMATION - NET SALES, EXCLUDING PRECIOUS METAL CONTENT (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total net sales, including precious metal content	$ 1,091.0	$ 1,009.2	$ 992.7	$ 900.5	$ 996.5	$ 954.2	$ 1,022.0	$ 772.6	$ 3,993.4	$ 3,745.3	$ 2,674.3
Technologies & Equipment
Segment Reporting Information [Line Items]
Total net sales, including precious metal content									2,200.8	2,050.5	1,112.7
Consumables
Segment Reporting Information [Line Items]
Total net sales, including precious metal content									1,792.6	1,694.8	1,561.6
Operating Segments
Segment Reporting Information [Line Items]
Total net sales, including precious metal content									3,952.9	3,681.0	2,581.5
Operating Segments | Technologies & Equipment
Segment Reporting Information [Line Items]
Total net sales, including precious metal content									2,160.3	1,986.4	1,019.9
Operating Segments | Consumables
Segment Reporting Information [Line Items]
Total net sales, including precious metal content									1,792.6	1,694.6	1,561.6
Segment Reconciling Items
Segment Reporting Information [Line Items]
Total net sales, including precious metal content									$ 40.5	$ 64.3	$ 92.8