SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Significant Noncash Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Significant Noncash Transactions [Line Items]
Unrealized loss on available-for-sale securities	$ (129)	$ (7)	$ (10)
Cash paid for income taxes	10,400	8,000	6,600
Common stock issued to Board of Directors and Scientific Advisory Board that was earned in a previous period [Member]
Other Significant Noncash Transactions [Line Items]
Other non-cash activities	300	323	315
Common stock issued to employees that was accrued for in a previous period, net of shares withheld for taxes [Member]
Other Significant Noncash Transactions [Line Items]
Other non-cash activities	967	749	282
Other Capitalized Property Plant and Equipment [Member]
Other Significant Noncash Transactions [Line Items]
Other non-cash activities	$ 467	$ 965	$ 420