NET INCOME (LOSS) PER SHARE - Narrative (Details) - shares shares in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock options and restricted stock units
Schedule of Earnings Per Share [Line Items]
Total number of options to purchase common stock and restricted stock units, outstanding (in shares)	1.2	2.3	4.7