STOCK-BASED COMPENSATION - RESTRICTED SHARE UNITS (Details) (Restricted Share Units, USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Share Units
Restricted Share Unit Awards
Outstanding at the beginning of the period (in shares)	67,741
Granted (in shares)	28,725
Dividend equivalents (in shares)	2,875
Vested and released (in shares)	(28,325)
Transfers (in shares)	332
Forfeited (in shares)	(804)
Outstanding at the end of the period (in shares)	70,544	67,741
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 52.06
Granted (in dollars per share)	$ 55.23	$ 56.05	$ 53.24
Dividend equivalents (in dollars per share)	$ 54.45
Vested and released (in dollars per share)	$ 49.50
Transfers (in dollars per share)	$ 54.55
Forfeited (in dollars per share)	$ 54.64
Outstanding at the end of the period (in dollars per share)	$ 54.46	$ 52.06
Additional Disclosures
Compensation cost not yet recognized	$ 3.5
Weighted-average period over which compensation cost is to be recognized	2 years 4 months
Total intrinsic value of restricted share units vested and released	$ 1.5	$ 1.6	$ 1.5