REVENUE RECOGNITION - Additional disclosures (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Customer Frequency Program
Deferred revenues and income	$ 449.2	$ 414.8	$ 391.0
Gift Card And Ticket Exchange
Customer Frequency Program
Redemption period	24 months
Deferred revenues and income	$ 354.3
Loyalty Program
Customer Frequency Program
Redemption period	24 months
Deferred revenues and income	$ 57.4
Exhibitor Services Agreement
Customer Frequency Program
Expected to be recognized as revenue	549.7
Exhibitor Services Agreement \| Year Ended 2020
Customer Frequency Program
Expected to be recognized as revenue	16.9
Exhibitor Services Agreement \| Year Ended 2021
Customer Frequency Program
Expected to be recognized as revenue	18.1
Exhibitor Services Agreement \| Year Ended 2022
Customer Frequency Program
Expected to be recognized as revenue	19.5
Exhibitor Services Agreement \| Year Ended 2023
Customer Frequency Program
Expected to be recognized as revenue	20.9
Exhibitor Services Agreement \| Year Ended 2024
Customer Frequency Program
Expected to be recognized as revenue	22.5
Exhibitor Services Agreement \| Years Ended 2025 through February 2037
Customer Frequency Program
Expected to be recognized as revenue	$ 451.8