SHARE-BASED COMPENSATION - Stock Options Activity (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at the beginning of year (in shares)	630,680		660,333	714,866
Granted (in shares)	75,780		85,930	116,119
Exercised (in shares)	(131,974)		(74,430)	(143,652)
Forfeited (in shares)	(50,708)		(41,153)	(27,000)
Canceled (in shares)				0
Options outstanding at the end of year (in shares)	523,778		630,680	660,333
Options vested and exercisable as of December 31, 2014 (in shares)	293,231
Remaining options expected to vest as of December 31, 2014 (in shares)	215,337
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price at the beginning of year (in dollars per share)	$ 32.31		$ 25.60	$ 20.89
Granted (in dollars per share)	$ 73.75		$ 72.42	$ 42.69
Exercised (in dollars per share)	$ 24.41		$ 20.62	$ 17.50
Forfeited (in dollars per share)	$ 44.02		$ 29.61	$ 17.50
Canceled (in dollars per share)				$ 0.00
Weighted Average Exercise Price at the end of year (in dollars per share)	$ 39.16		$ 32.31	$ 25.60
Options vested and exercisable as of December 31, 2014, Weighted Average Exercise Price (in dollars per share)	$ 30.33
Remaining options expected to vest as of December 31, 2014, Weighted Average Exercise Price (in dollars per share)	$ 49.28
Weighted Average Remaining Contractual Term (in years)	7 years
Options vested and exercisable as of December 31, 2014, Weighted Average Remaining Contractual Term (in years)	6 years 4 months 24 days
Remaining options expected to vest as of December 31, 2014, Weighted Average Remaining Contractual Term (in years)	7 years 9 months 18 days
Aggregate Intrinsic Value (in millions)	$ 7.4		$ 3.7	$ 6.4
Options vested and exercisable as of December 31, 2014, Aggregate Intrinsic Value	15.0	[1]
Remaining options expected to vest as of December 31, 2014, Aggregate Intrinsic Value	$ 6.9	[1]

[1] The aggregate intrinsic value of options represents the total pre-tax intrinsic value (the difference between the estimated fair value of the Company's stock on December 31, 2014 and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on December 31, 2014. This amount changes based upon the fair market value of the Company's common stock.