SHAREHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2004	Dec. 31, 2016	Dec. 31, 2015
Option Exercises
Options exercised during period (in shares)		711,863	1,141,345
Net proceeds from options exercised during the period		$ 6.7	$ 7.9
ESPP
Shareholders' equity
Number of shares authorized for issuance		3,000,000
Number of shares available for future issuance		670,618
Shares sold		201,264	164,674
Weighted average purchase price of shares sold (in dollars per share)		$ 16.19	$ 14.95
Proceeds from shares sold		$ 3.3	$ 2.5
ESPP | Minimum
Shareholders' equity
Purchase price expressed as percentage of fair market value of common stock	85.00%