STOCK-BASED COMPENSATION - SUMMARY OF STOCK-BASED COMPENSATION EXPENSE (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 47.7		$ 42.5
Stock-based compensation expense capitalized as property and equipment	0.5		0.5
Stock-based compensation expense Property
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	0.6		0.6
Service
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	0.3		0.3
Stock-based compensation expense SG&A
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 46.8	$ 41.6	$ 41.6