INCOME TAXES - Loss Carryforwards (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($) item $ / shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017
Operating loss carryforwards
Statutory U.S. rate (as a percent)	21.00%	21.00%	21.00%	35.00%
Net discrete expense (benefit), prior year returns		$ 11.0	$ (39.5)
Net operating loss carryforwards	$ 63.4	48.0
Valuation allowance on deferred tax asset	45.3	$ 24.5
Number of foreign jurisdictions with a tax holiday | item		2
Federal
Operating loss carryforwards
Net operating loss carryforwards	0.1
Carryforwards subject to expiration	20.3
State
Operating loss carryforwards
Net operating loss carryforwards	20.2
International
Operating loss carryforwards
Net operating loss carryforwards	43.1
Carryforwards subject to expiration	13.9
No expiration	29.2
Preferential income tax rate, certain headquarter income		10.00%
Tax reduction due to tax holiday	$ 26.9	$ 29.2	$ 25.6
Tax holiday impact on diluted earnings per share (in dollars per share) | $ / shares	$ 0.09	$ 0.10	$ 0.09