SHAREHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	12 Months Ended
	Jul. 12, 2015	May. 31, 2004	Dec. 31, 2015	Dec. 31, 2014
Option Exercises
Options exercised during period (in shares)			1,141,345	1,515,023
Net proceeds from options exercised during the period			$ 7.9	$ 8.4
Series B Junior Participating Preferred Stock
Rights Plan
Dividends declared as rights per share	1
Number of shares that each right entitles the holder to purchase	0.01
Purchase price per fractional share	$ 105.00
Number of days on which beneficial ownership is ten percent or more of outstanding share.	10 days
Beneficial ownership (as a percent)	10.00%
Number of business days from commencement of tender or exchange offer	10 days
ESPP
Shareholders' equity
Number of shares authorized for issuance			2,500,000
Number of shares available for future issuance			371,882
Shares sold			164,674	177,036
Weighted average purchase price of shares sold (in dollars per share)			$ 14.95	$ 8.68
Proceeds from shares sold			$ 2.5	$ 1.5
ESPP | Minimum
Shareholders' equity
Purchase price expressed as percentage of fair market value of common stock		85.00%