STOCK-BASED COMPENSATION - 2012 Plan and ESPP (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) item shares
Employee Stock Purchase Plan
Stock-based compensation
Purchase price as a percentage of fair market value of stock	85.00%
Total duration of consecutive and overlapping offering periods	24 months
Number of offering periods | item	4
Duration of purchase period	6 months
Maximum contributions as a percentage of employee's eligible compensation	15.00%
Maximum number of shares an employee may purchase during any purchase period	2,500
Maximum value of shares an employee may purchase in a calendar year | $	$ 25,000
Shares remaining available for issuance	237,627
2012 Equity Incentive Plan
Stock-based compensation
Shares remaining available for issuance	3,573,436