STOCK-BASED COMPENSATION - Plans (Details) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2017 shares	Sep. 30, 2017 shares	Jun. 30, 2017 shares	Mar. 31, 2017 shares	Dec. 31, 2017 USD ($) plan shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Stock-based compensation
Stock-based compensation plans | plan					2
Compensation expense on share-based plans | $					$ 52.3	$ 45.8	$ 32.7
Stock options
Stock-based compensation
Common stock granted, net of cancellations (in shares)	77,000	12,000	26,000	1,319,000
Excess tax benefit realized for tax deductions from non-qualified stock option exercises and disqualifying dispositions of incentive stock options | $					$ 96.7	20.8	314.7
2011 Omnibus Incentive Plan
Stock-based compensation
Aggregate amount of common stock authorized (in shares)	43,500,000				43,500,000
Reduction in number of shares for each share granted	2.16				2.16
Common stock granted, net of cancellations (in shares)					19,978,932
Shares available for grant	19,651,474				19,651,474
2011 Omnibus Incentive Plan | Stock options
Stock-based compensation
Vesting period					5 years
2011 Omnibus Incentive Plan | Stock options | Maximum
Stock-based compensation
Expiration period (in years)					10 years
2017 Directors Plan
Stock-based compensation
Aggregate amount of common stock authorized (in shares)	1,250,000				1,250,000
Common stock granted, net of cancellations (in shares)					23,566
Shares available for grant	1,226,434				1,226,434
Number of common shares held and expected to vest for eligibility under plan	9,000				9,000
Adjustments for New Accounting Principle | Accounting Standards Update 2016-09: Simplifying the accounting for share-based compensation
Stock-based compensation
Excess tax benefit from stock based compensation | $					$ 96.7	$ 20.8
Adjustments to additional paid-in-capital, benefit associated with share-based compensation | $							$ 314.7